diff --git a/books/free-programming-books-ar.md b/books/free-programming-books-ar.md
index 3cadc5316..d99edea1c 100644
--- a/books/free-programming-books-ar.md
+++ b/books/free-programming-books-ar.md
@@ -10,12 +10,12 @@
 * [HTML/CSS](#htmlcss)
 * [Introduction to Programming in Arabic](#introduction-to-programming-in-arabic)
 * [JavaScript](#javascript)
-  * [Vue.js](#vuejs)
+    * [Vue.js](#vuejs)
 * [Linux](#linux)
 * [Open Source Software](#open-source-software)
 * [Operating System](#operating-systems)
 * [PHP](#php)
-  * [Symfony](#symfony)
+    * [Symfony](#symfony)
 * [Programming in Scratch](#programming-in-scratch)
 * [Python](#python)
 * [Raspberry Pi](#raspberry-pi)
@@ -23,7 +23,7 @@
 * [Security](#security)
 * [SEO](#seo)
 * [SQL](#sql)
-  * [PostgreSQL](#postgresql)
+    * [PostgreSQL](#postgresql)
 * [UI/UX](#uiux)
 
 
diff --git a/books/free-programming-books-cs.md b/books/free-programming-books-cs.md
index b1b8510e9..f0ed129bd 100644
--- a/books/free-programming-books-cs.md
+++ b/books/free-programming-books-cs.md
@@ -7,19 +7,19 @@
 * [HTML](#html)
 * [Java](#java)
 * [Language Agnostic](#language-agnostic)
-  * [Algoritmy a datové struktury](#algoritmy-a-datove-struktury)
-  * [Bezpečnost](#bezpecnost)
-  * [Matematika](#matematika)
-  * [Právo](#pravo)
-  * [Regulární výrazy](#regularni-vyrazy)
-  * [Sítě](#site)
+    * [Algoritmy a datové struktury](#algoritmy-a-datove-struktury)
+    * [Bezpečnost](#bezpecnost)
+    * [Matematika](#matematika)
+    * [Právo](#pravo)
+    * [Regulární výrazy](#regularni-vyrazy)
+    * [Sítě](#site)
 * [LaTeX](#latex)
 * [Linux](#linux)
   * [Distribuce](#distribuce)
 * [OpenSource](#opensource)
 * [PHP](#php)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 * [Ruby](#ruby)
 * [TeX](#tex)
 * [Unity](#unity)
diff --git a/books/free-programming-books-de.md b/books/free-programming-books-de.md
index b2abf6387..f42ae70b3 100644
--- a/books/free-programming-books-de.md
+++ b/books/free-programming-books-de.md
@@ -15,16 +15,16 @@
 * [iOS](#ios)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [React](#react)
+    * [React](#react)
 * [LaTeX](#latex)
 * [Mathematik](#mathematik)
 * [Meta-Lists](#meta-lists)
 * [MySQL](#mysql)
 * [Neo4j](#neo4j)
 * [PHP](#php)
-  * [Symfony](#symfony)
+    * [Symfony](#symfony)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 * [Ruby on Rails](#ruby-on-rails)
 * [Scilab](#scilab)
 * [Scratch](#scratch)
diff --git a/books/free-programming-books-es.md b/books/free-programming-books-es.md
index 4398ad790..7f890ec24 100644
--- a/books/free-programming-books-es.md
+++ b/books/free-programming-books-es.md
@@ -2,12 +2,12 @@
 
 * [0 - Meta-Listas](#0---meta-listas)
 * [1 - Agnósticos](#1---agnósticos)
-  * [Algoritmos y Estructuras de Datos](#algoritmos-y-estructuras-de-datos)
-  * [Base de Datos](#base-de-datos)
-  * [Ciencia Computacional](#ciencia-computacional)
-  * [Metodologías de Desarrollo de Software](#metodologías-de-desarrollo-de-software)
-  * [Misceláneos](#misceláneos)
-  * [Sistemas Operativos](#sistemas-operativos)
+    * [Algoritmos y Estructuras de Datos](#algoritmos-y-estructuras-de-datos)
+    * [Base de Datos](#base-de-datos)
+    * [Ciencia Computacional](#ciencia-computacional)
+    * [Metodologías de Desarrollo de Software](#metodologías-de-desarrollo-de-software)
+    * [Misceláneos](#misceláneos)
+    * [Sistemas Operativos](#sistemas-operativos)
 * [Android](#android)
 * [C](#c)
 * [C++](#cpp)
@@ -21,35 +21,35 @@
 * [HTML & CSS](#html--css)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
-  * [D3](#d3js)
-  * [jQuery](#jquery)
-  * [node.js](#nodejs)
-  * [React](#react)
+    * [AngularJS](#angularjs)
+    * [D3](#d3js)
+    * [jQuery](#jquery)
+    * [node.js](#nodejs)
+    * [React](#react)
 * [LaTeX](#latex)
 * [Linux](#linux)
 * [Matemáticas](#matem%C3%A1ticas)
 * [.NET (C# Visual Studio)](#net-c--visual-studio)
 * [NoSQL](#nosql)
-  * [MongoDB](#mongodb)
-  * [Redis](#redis)
+    * [MongoDB](#mongodb)
+    * [Redis](#redis)
 * [Perl](#perl)
 * [Perl 6 / Raku](#perl-6--raku)
 * [PHP](#php)
-  * [Symfony](#symfony)
+    * [Symfony](#symfony)
 * [Python](#python)
-  * [Django](#django)
-  * [Web2py](#web2py)
+    * [Django](#django)
+    * [Web2py](#web2py)
 * [R](#r)
 * [Ruby](#ruby)
-  * [Ruby on Rails](#ruby-on-rails)
+    * [Ruby on Rails](#ruby-on-rails)
 * [Scala](#scala)
 * [Scratch](#scratch)
 * [SQL](#sql)
 * [Subversion](#subversion)
 * [SVG](#svg)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 
 
 ### 0 - Meta-Listas
diff --git a/books/free-programming-books-et.md b/books/free-programming-books-et.md
index c56f8810d..1c356aa8d 100644
--- a/books/free-programming-books-et.md
+++ b/books/free-programming-books-et.md
@@ -5,8 +5,8 @@
 * [C#](#csharp)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
-  * [Vue](#vue)
+    * [AngularJS](#angularjs)
+    * [Vue](#vue)
 * [PHP](#php)
 * [Python](#python)
 * [R](#r)
diff --git a/books/free-programming-books-fa_IR.md b/books/free-programming-books-fa_IR.md
index 1174bf998..9874ef559 100644
--- a/books/free-programming-books-fa_IR.md
+++ b/books/free-programming-books-fa_IR.md
@@ -8,7 +8,7 @@
 * [LaTeX](#latex)
 * [Linux](#linux)
 * [PHP](#php)
-  * [Symfony](#symfony)
+    * [Symfony](#symfony)
 * [Python](#python)
 * [R](#r)
 
diff --git a/books/free-programming-books-fr.md b/books/free-programming-books-fr.md
index d5403a85d..99fe44b02 100644
--- a/books/free-programming-books-fr.md
+++ b/books/free-programming-books-fr.md
@@ -2,11 +2,11 @@
 
 * [0 - Méta-listes](#0---méta-listes)
 * [1 - Non dépendant du langage](#1---non-dépendant-du-langage)
-  * [Algorithmique](#algorithmique)
-  * [Logiciels libres](#logiciels-libres)
-  * [Makefile](#makefile)
-  * [Pédagogie pour enfants et adolescents](#pédagogie-pour-enfants-et-adolescents)
-  * [Théorie des langages](#théorie-des-langages)
+    * [Algorithmique](#algorithmique)
+    * [Logiciels libres](#logiciels-libres)
+    * [Makefile](#makefile)
+    * [Pédagogie pour enfants et adolescents](#pédagogie-pour-enfants-et-adolescents)
+    * [Théorie des langages](#théorie-des-langages)
 * [Ada](#ada)
 * [Assembleur](#assembleur)
 * [Bash / Shell](#bash--shell)
@@ -22,21 +22,21 @@
 * [JavaScript](#javascript)
 * [jQuery](#jquery)
 * [(La)TeX et associés](#latex-et-associés)
-  * [Asymptote](#asymptote)
-  * [LaTeX](#latex)
-  * [Metapost](#metapost)
-  * [PGF/TikZ](#pgftikz)
-  * [TeX](#tex)
+    * [Asymptote](#asymptote)
+    * [LaTeX](#latex)
+    * [Metapost](#metapost)
+    * [PGF/TikZ](#pgftikz)
+    * [TeX](#tex)
 * [Lisp](#lisp)
 * [Lua](#lua)
 * [Mathématiques](#math%C3%A9matiques)
 * [Meteor](#meteor)
 * [Perl](#perl)
 * [PHP](#php)
-  * [Symfony](#symfony)
+    * [Symfony](#symfony)
 * [Processing](#processing)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 * [R](#r)
 * [Ruby](#ruby)
 * [Rust](#rust)
@@ -140,9 +140,9 @@
 
 * [IDRIS adaptation of the Fortran 77 manual](http://www.idris.fr/formations/fortran/fortran-77.html) - IDRIS, Hervé Delouis, Patrick Corde (HTML)
 * [IDRIS Formations Fortran: documentation](http://www.idris.fr/formations/fortran/) (HTML)
-  * [Fortran_Avancé : "Fortran : apports des normes 90 et 95 avec quelques aspects de la norme 2003" (2ème niveau)](http://www.idris.fr/media/formations/fortran/idris_fortran_avance_cours.pdf) - Patrick Corde, Hervé Delouis (PDF) ([:package: travaux pratiques](http://www.idris.fr/media/formations/fortran/idris_fortran_avance_tp.tar.gz))
-  * [Fortran_Base : "Fortran : notions de base" (1er niveau)](http://www.idris.fr/media/formations/fortran/idris_fortran_base_cours.pdf) - Anne Fouilloux, Patrick Corde (PDF) ([:package: examples du support](http://www.idris.fr/media/formations/fortran/idris_fortran_base_exemples.tar.gz), [:package: travaux pratiques](http://www.idris.fr/media/formations/fortran/idris_fortran_base_tp.tar.gz))
-  * [Fortran_Expert : "Fortran : apports de la norme 2003 avec quelques aspects de la norme 2008"](http://www.idris.fr/media/formations/fortran/idris_fortran_expert_cours.pdf) - Patrick Corde, Hervé Delouis (PDF) ([:package: examples du support](http://www.idris.fr/media/formations/fortran/idris_fortran_expert_exemples.tar.gz), [:package: travaux pratiques](http://www.idris.fr/media/formations/fortran/idris_fortran_expert_tp.tar.gz))
+    * [Fortran_Avancé : "Fortran : apports des normes 90 et 95 avec quelques aspects de la norme 2003" (2ème niveau)](http://www.idris.fr/media/formations/fortran/idris_fortran_avance_cours.pdf) - Patrick Corde, Hervé Delouis (PDF) ([:package: travaux pratiques](http://www.idris.fr/media/formations/fortran/idris_fortran_avance_tp.tar.gz))
+    * [Fortran_Base : "Fortran : notions de base" (1er niveau)](http://www.idris.fr/media/formations/fortran/idris_fortran_base_cours.pdf) - Anne Fouilloux, Patrick Corde (PDF) ([:package: examples du support](http://www.idris.fr/media/formations/fortran/idris_fortran_base_exemples.tar.gz), [:package: travaux pratiques](http://www.idris.fr/media/formations/fortran/idris_fortran_base_tp.tar.gz))
+    * [Fortran_Expert : "Fortran : apports de la norme 2003 avec quelques aspects de la norme 2008"](http://www.idris.fr/media/formations/fortran/idris_fortran_expert_cours.pdf) - Patrick Corde, Hervé Delouis (PDF) ([:package: examples du support](http://www.idris.fr/media/formations/fortran/idris_fortran_expert_exemples.tar.gz), [:package: travaux pratiques](http://www.idris.fr/media/formations/fortran/idris_fortran_expert_tp.tar.gz))
 
 
 ### Git
diff --git a/books/free-programming-books-he.md b/books/free-programming-books-he.md
index beb7a747e..7d74b2339 100644
--- a/books/free-programming-books-he.md
+++ b/books/free-programming-books-he.md
@@ -1,8 +1,8 @@
 ### Index
 
 * [ללא תלות בשפה](#ללא-תלות-בשפה)
-  * [מערכות הפעלה](#מערכות-הפעלה)
-  * [רשתות](#רשתות)
+    * [מערכות הפעלה](#מערכות-הפעלה)
+    * [רשתות](#רשתות)
 * [Assembly](#assembly)
 * [C#](#csharp)
 * [Java](#java)
diff --git a/books/free-programming-books-hu.md b/books/free-programming-books-hu.md
index b0b146739..25fc68ff4 100644
--- a/books/free-programming-books-hu.md
+++ b/books/free-programming-books-hu.md
@@ -13,7 +13,7 @@
 * [PHP](#php)
 * [PowerShell](#powershell)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 * [Windows Phone](#windows-phone)
 
 
diff --git a/books/free-programming-books-id.md b/books/free-programming-books-id.md
index 1f29c57ac..80356c0fe 100644
--- a/books/free-programming-books-id.md
+++ b/books/free-programming-books-id.md
@@ -21,8 +21,8 @@
 * [React](#react)
 * [Solidity](#solidity)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
-  * [Deno](#deno)
+    * [Angular](#angular)
+    * [Deno](#deno)
 * [Vue](#vue)
 
 
diff --git a/books/free-programming-books-it.md b/books/free-programming-books-it.md
index 8cff7ae81..1d8b96fa8 100644
--- a/books/free-programming-books-it.md
+++ b/books/free-programming-books-it.md
@@ -1,12 +1,12 @@
 ### Index
 
 * [0 - Agnostico](#0---agnostico)
-  * [Algoritmi e Strutture Dati](#algoritmi-e-strutture-dati)
-  * [Metodologie di sviluppo del software](#metodologie-di-sviluppo-del-software)
-  * [Open source](#open-source)
-  * [Sistemi](#sistemi)
-  * [Sistemi di controllo versione](#sistemi-di-controllo-versione)
-  * [Storia dell'informatica](#storia-dellinformatica)
+    * [Algoritmi e Strutture Dati](#algoritmi-e-strutture-dati)
+    * [Metodologie di sviluppo del software](#metodologie-di-sviluppo-del-software)
+    * [Open source](#open-source)
+    * [Sistemi](#sistemi)
+    * [Sistemi di controllo versione](#sistemi-di-controllo-versione)
+    * [Storia dell'informatica](#storia-dellinformatica)
 * [Android](#android)
 * [Assembly Language](#assembly-language)
 * [BASH](#bash)
@@ -15,27 +15,27 @@
 * [C++](#cpp)
 * [CSS](#css)
 * [Database](#database)
-  * [NoSQL](#nosql)
-  * [Relazionali](#relazionali)
-  * [SQL](#sql)
+    * [NoSQL](#nosql)
+    * [Relazionali](#relazionali)
+    * [SQL](#sql)
 * [Git](#git)
 * [Golang](#golang)
 * [HTML](#html)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
+    * [AngularJS](#angularjs)
 * [Kotlin](#kotlin)
 * [LaTeX](#latex)
 * [Linux](#linux)
 * [Livecode](#livecode)
 * [Perl](#perl)
 * [PHP](#php)
-  * [Symfony](#symfony)
+    * [Symfony](#symfony)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 * [Ruby](#ruby)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 * [UML](#uml)
 * [Visual Basic](#visual-basic)
 
diff --git a/books/free-programming-books-ja.md b/books/free-programming-books-ja.md
index ca39b97cf..019f2edae 100644
--- a/books/free-programming-books-ja.md
+++ b/books/free-programming-books-ja.md
@@ -1,24 +1,24 @@
 ### Index
 
 * [0 - 言語非依存](#0---%e8%a8%80%e8%aa%9e%e9%9d%9e%e4%be%9d%e5%ad%98)
-  * [アクセシビリティ](#%e3%82%a2%e3%82%af%e3%82%bb%e3%82%b7%e3%83%93%e3%83%aa%e3%83%86%e3%82%a3)
-  * [オープンソースエコシステム](#%e3%82%aa%e3%83%bc%e3%83%97%e3%83%b3%e3%82%bd%e3%83%bc%e3%82%b9%e3%82%a8%e3%82%b3%e3%82%b7%e3%82%b9%e3%83%86%e3%83%a0)
-  * [ガベージコレクション](#%e3%82%ac%e3%83%99%e3%83%bc%e3%82%b8%e3%82%b3%e3%83%ac%e3%82%af%e3%82%b7%e3%83%a7%e3%83%b3)
-  * [グラフィックスプログラミング](#%e3%82%b0%e3%83%a9%e3%83%95%e3%82%a3%e3%83%83%e3%82%af%e3%82%b9%e3%83%97%e3%83%ad%e3%82%b0%e3%83%a9%e3%83%9f%e3%83%b3%e3%82%b0)
-  * [グラフィックユーザーインターフェイス](#%e3%82%b0%e3%83%a9%e3%83%95%e3%82%a3%e3%83%83%e3%82%af%e3%83%a6%e3%83%bc%e3%82%b6%e3%83%bc%e3%82%a4%e3%83%b3%e3%82%bf%e3%83%bc%e3%83%95%e3%82%a7%e3%82%a4%e3%82%b9)
-  * [コンテナ](#%E3%82%B3%E3%83%B3%E3%83%86%E3%83%8A)
-  * [セキュリティ](#%e3%82%bb%e3%82%ad%e3%83%a5%e3%83%aa%e3%83%86%e3%82%a3)
-  * [その他の話題](#%e3%81%9d%e3%81%ae%e4%bb%96%e3%81%ae%e8%a9%b1%e9%a1%8c)
-  * [ソフトウェアアーキテクチャ](#%e3%82%bd%e3%83%95%e3%83%88%e3%82%a6%e3%82%a7%e3%82%a2%e3%82%a2%e3%83%bc%e3%82%ad%e3%83%86%e3%82%af%e3%83%81%e3%83%a3)
-  * [ソフトウェア開発方法論](#%e3%82%bd%e3%83%95%e3%83%88%e3%82%a6%e3%82%a7%e3%82%a2%e9%96%8b%e7%99%ba%e6%96%b9%e6%b3%95%e8%ab%96)
-  * [ソフトウェア品質](#%e3%82%bd%e3%83%95%e3%83%88%e3%82%a6%e3%82%a7%e3%82%a2%e5%93%81%e8%b3%aa)
-  * [データベース](#%e3%83%87%e3%83%bc%e3%82%bf%e3%83%99%e3%83%bc%e3%82%b9)
-  * [ネットワーキング](#%e3%83%8d%e3%83%83%e3%83%88%e3%83%af%e3%83%bc%e3%82%ad%e3%83%b3%e3%82%b0)
-  * [機械学習](#%e6%a9%9f%e6%a2%b0%e5%ad%a6%e7%bf%92)
-  * [正規表現](#%e6%ad%a3%e8%a6%8f%e8%a1%a8%e7%8f%be)
-  * [組み込みシステム](#%e7%b5%84%e3%81%bf%e8%be%bc%e3%81%bf%e3%82%b7%e3%82%b9%e3%83%86%e3%83%a0)
-  * [並列プログラミング](#%e4%b8%a6%e5%88%97%e3%83%97%e3%83%ad%e3%82%b0%e3%83%a9%e3%83%9f%e3%83%b3%e3%82%b0)
-  * [理論計算機科学](#%e7%90%86%e8%ab%96%e8%a8%88%e7%ae%97%e6%a9%9f%e7%a7%91%e5%ad%a6)
+    * [アクセシビリティ](#%e3%82%a2%e3%82%af%e3%82%bb%e3%82%b7%e3%83%93%e3%83%aa%e3%83%86%e3%82%a3)
+    * [オープンソースエコシステム](#%e3%82%aa%e3%83%bc%e3%83%97%e3%83%b3%e3%82%bd%e3%83%bc%e3%82%b9%e3%82%a8%e3%82%b3%e3%82%b7%e3%82%b9%e3%83%86%e3%83%a0)
+    * [ガベージコレクション](#%e3%82%ac%e3%83%99%e3%83%bc%e3%82%b8%e3%82%b3%e3%83%ac%e3%82%af%e3%82%b7%e3%83%a7%e3%83%b3)
+    * [グラフィックスプログラミング](#%e3%82%b0%e3%83%a9%e3%83%95%e3%82%a3%e3%83%83%e3%82%af%e3%82%b9%e3%83%97%e3%83%ad%e3%82%b0%e3%83%a9%e3%83%9f%e3%83%b3%e3%82%b0)
+    * [グラフィックユーザーインターフェイス](#%e3%82%b0%e3%83%a9%e3%83%95%e3%82%a3%e3%83%83%e3%82%af%e3%83%a6%e3%83%bc%e3%82%b6%e3%83%bc%e3%82%a4%e3%83%b3%e3%82%bf%e3%83%bc%e3%83%95%e3%82%a7%e3%82%a4%e3%82%b9)
+    * [コンテナ](#%E3%82%B3%E3%83%B3%E3%83%86%E3%83%8A)
+    * [セキュリティ](#%e3%82%bb%e3%82%ad%e3%83%a5%e3%83%aa%e3%83%86%e3%82%a3)
+    * [その他の話題](#%e3%81%9d%e3%81%ae%e4%bb%96%e3%81%ae%e8%a9%b1%e9%a1%8c)
+    * [ソフトウェアアーキテクチャ](#%e3%82%bd%e3%83%95%e3%83%88%e3%82%a6%e3%82%a7%e3%82%a2%e3%82%a2%e3%83%bc%e3%82%ad%e3%83%86%e3%82%af%e3%83%81%e3%83%a3)
+    * [ソフトウェア開発方法論](#%e3%82%bd%e3%83%95%e3%83%88%e3%82%a6%e3%82%a7%e3%82%a2%e9%96%8b%e7%99%ba%e6%96%b9%e6%b3%95%e8%ab%96)
+    * [ソフトウェア品質](#%e3%82%bd%e3%83%95%e3%83%88%e3%82%a6%e3%82%a7%e3%82%a2%e5%93%81%e8%b3%aa)
+    * [データベース](#%e3%83%87%e3%83%bc%e3%82%bf%e3%83%99%e3%83%bc%e3%82%b9)
+    * [ネットワーキング](#%e3%83%8d%e3%83%83%e3%83%88%e3%83%af%e3%83%bc%e3%82%ad%e3%83%b3%e3%82%b0)
+    * [機械学習](#%e6%a9%9f%e6%a2%b0%e5%ad%a6%e7%bf%92)
+    * [正規表現](#%e6%ad%a3%e8%a6%8f%e8%a1%a8%e7%8f%be)
+    * [組み込みシステム](#%e7%b5%84%e3%81%bf%e8%be%bc%e3%81%bf%e3%82%b7%e3%82%b9%e3%83%86%e3%83%a0)
+    * [並列プログラミング](#%e4%b8%a6%e5%88%97%e3%83%97%e3%83%ad%e3%82%b0%e3%83%a9%e3%83%9f%e3%83%b3%e3%82%b0)
+    * [理論計算機科学](#%e7%90%86%e8%ab%96%e8%a8%88%e7%ae%97%e6%a9%9f%e7%a7%91%e5%ad%a6)
 * [Android](#android)
 * [AppleScript](#applescript)
 * [Assembly](#assembly)
@@ -37,18 +37,18 @@
 * [Git](#git)
 * [Go](#go)
 * [Groovy](#groovy)
-  * [Gradle](#gradle)
-  * [Grails](#grails)
-  * [Spock Framework](#spock-framework)
+    * [Gradle](#gradle)
+    * [Grails](#grails)
+    * [Spock Framework](#spock-framework)
 * [Haskell](#haskell)
 * [iOS](#ios)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
-  * [Backbone.js](#backbonejs)
-  * [jQuery](#jquery)
-  * [Node.js](#nodejs)
-  * [React](#react)
+    * [AngularJS](#angularjs)
+    * [Backbone.js](#backbonejs)
+    * [jQuery](#jquery)
+    * [Node.js](#nodejs)
+    * [React](#react)
 * [Julia](#julia)
 * [LaTeX](#latex)
 * [Linux](#linux)
@@ -61,12 +61,12 @@
 * [OCaml](#ocaml)
 * [Perl](#perl)
 * [PHP](#php)
-  * [Symfony](#symfony)
+    * [Symfony](#symfony)
 * [PowerShell](#powershell)
 * [Processing](#processing)
 * [Prolog](#prolog)
 * [Python](#python)
-  * [Flask](#flask)
+    * [Flask](#flask)
 * [R](#r)
 * [Ruby](#ruby)
 * [Rust](#rust)
@@ -81,7 +81,7 @@
 * [Swift](#swift)
 * [Tcl/Tk](#tcltk)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 * [VBA](#vba)
 * [Vim](#vim)
 
diff --git a/books/free-programming-books-ko.md b/books/free-programming-books-ko.md
index 92810cf4b..63c3119b7 100644
--- a/books/free-programming-books-ko.md
+++ b/books/free-programming-books-ko.md
@@ -12,18 +12,18 @@
 * [HTML5](#html5)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [Node.js](#nodejs)
-  * [Webpack](#webpack)
+    * [Node.js](#nodejs)
+    * [Webpack](#webpack)
 * [LaTeX](#latex)
 * [Linux](#linux)
 * [Mathematics](#mathematics)
 * [Operation System](#operation-system)
 * [Perl](#perl)
 * [PHP](#php)
-  * [Laravel](#laravel)
+    * [Laravel](#laravel)
 * [Python](#python)
-  * [Django](#django)
-  * [Flask](#flask)
+    * [Django](#django)
+    * [Flask](#flask)
 * [R](#r)
 * [Raspberry Pi](#raspberry-pi)
 * [Ruby](#ruby)
diff --git a/books/free-programming-books-langs.md b/books/free-programming-books-langs.md
index c929f5f2e..cb38b5ced 100644
--- a/books/free-programming-books-langs.md
+++ b/books/free-programming-books-langs.md
@@ -16,9 +16,9 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Arduino](#arduino)
 * [ASP.NET](#aspnet)
 * [ASP.NET Core](#aspnet-core)
-  * [Blazor](#blazor)
+    * [Blazor](#blazor)
 * [Assembly Language](#assembly-language)
-  * [Non-X86](#non-x86)
+    * [Non-X86](#non-x86)
 * [AutoHotkey](#autohotkey)
 * [AutoIt](#autoit)
 * [Autotools](#autotools)
@@ -50,8 +50,8 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [DTrace](#dtrace)
 * [Eiffel](#eiffel)
 * [Elixir](#elixir)
-  * [Ecto](#ecto)
-  * [Phoenix](#phoenix)
+    * [Ecto](#ecto)
+    * [Phoenix](#phoenix)
 * [Elm](#elm)
 * [Emacs](#emacs)
 * [Embedded Systems](#embedded-systems)
@@ -67,16 +67,16 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Go](#go)
 * [GraphQL](#graphql)
 * [Groovy](#groovy)
-  * [Gradle](#gradle)
-  * [Grails](#grails)
-  * [Spock Framework](#spock-framework)
+    * [Gradle](#gradle)
+    * [Grails](#grails)
+    * [Spock Framework](#spock-framework)
 * [Hack](#hack)
 * [Hadoop](#hadoop)
 * [Haskell](#haskell)
 * [Haxe](#haxe)
 * [HTML / CSS](#html--css)
-  * [Bootstrap](#bootstrap)
-  * [Tailwindcss](https://tailwindcss.com/docs) - Adam Wathan
+    * [Bootstrap](#bootstrap)
+    * [Tailwindcss](https://tailwindcss.com/docs) - Adam Wathan
 * [HTTP](#http)
 * [HTTPS](#https)
 * [Icon](#icon)
@@ -86,43 +86,43 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Isabelle/HOL](#isabellehol)
 * [J](#j)
 * [Java](#java)
-  * [Codename One](#codename-one)
-  * [Java Reporting](#java-reporting)
-  * [Spring](#spring)
-  * [Spring Boot](#spring-boot)
-  * [Spring Data](#spring-data)
-  * [Spring Security](#spring-security)
-  * [Wicket](#wicket)
+    * [Codename One](#codename-one)
+    * [Java Reporting](#java-reporting)
+    * [Spring](#spring)
+    * [Spring Boot](#spring-boot)
+    * [Spring Data](#spring-data)
+    * [Spring Security](#spring-security)
+    * [Wicket](#wicket)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
-  * [Aurelia](#aurelia)
-  * [Backbone.js](#backbonejs)
-  * [Booty5.js](#booty5js)
-  * [D3.js](#d3js)
-  * [Dojo](#dojo)
-  * [Electron](#electron)
-  * [Elm](#elm)
-  * [Ember.js](#emberjs)
-  * [Express.js](#expressjs)
-  * [Fastify](#fastify)
-  * [Ionic](#ionic)
-  * [jQuery](#jquery)
-  * [meteor](#meteor)
-  * [Next.js](#next.js)
-  * [Node.js](#nodejs)
-  * [Om](#om)
-  * [React](#react)
-  * [React Native](#react-native)
-  * [Redux](#redux)
-  * [Svelte](#svelte)
-  * [Vue.js](#vuejs)
+    * [AngularJS](#angularjs)
+    * [Aurelia](#aurelia)
+    * [Backbone.js](#backbonejs)
+    * [Booty5.js](#booty5js)
+    * [D3.js](#d3js)
+    * [Dojo](#dojo)
+    * [Electron](#electron)
+    * [Elm](#elm)
+    * [Ember.js](#emberjs)
+    * [Express.js](#expressjs)
+    * [Fastify](#fastify)
+    * [Ionic](#ionic)
+    * [jQuery](#jquery)
+    * [meteor](#meteor)
+    * [Next.js](#next.js)
+    * [Node.js](#nodejs)
+    * [Om](#om)
+    * [React](#react)
+    * [React Native](#react-native)
+    * [Redux](#redux)
+    * [Svelte](#svelte)
+    * [Vue.js](#vuejs)
 * [Jenkins](#jenkins)
 * [Julia](#julia)
 * [Kotlin](#kotlin)
 * [Language Agnostic](free-programming-books-subjects.md)
 * [LaTeX / TeX](#latex--tex)
-  * [LaTeX](#latex)
-  * [TeX](#tex)
+    * [LaTeX](#latex)
+    * [TeX](#tex)
 * [Limbo](#limbo)
 * [Linux](#linux)
 * [Lisp](#lisp)
@@ -152,26 +152,26 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [OpenSCAD](#openscad)
 * [Perl](#perl)
 * [PHP](#php)
-  * [CakePHP](#cakephp)
-  * [CodeIgniter](#codeigniter)
-  * [Drupal](#drupal)
-  * [Laravel](#laravel)
-  * [Symfony](#symfony)
-  * [Zend](#zend)
+    * [CakePHP](#cakephp)
+    * [CodeIgniter](#codeigniter)
+    * [Drupal](#drupal)
+    * [Laravel](#laravel)
+    * [Symfony](#symfony)
+    * [Zend](#zend)
 * [PicoLisp](#picolisp)
 * [PostgreSQL](#postgresql)
 * [PowerShell](#powershell)
 * [Processing](#processing)
 * [Prolog](#prolog)
-  * [Constraint Logic Programming](#constraint-logic-programming-extended-prolog)
+    * [Constraint Logic Programming](#constraint-logic-programming-extended-prolog)
 * [PureScript](#purescript)
 * [Python](#python)
-  * [Django](#django)
-  * [Flask](#flask)
-  * [Kivy](#kivy)
-  * [Pandas](#pandas)
-  * [Pyramid](#pyramid)
-  * [Tornado](#tornado)
+    * [Django](#django)
+    * [Flask](#flask)
+    * [Kivy](#kivy)
+    * [Pandas](#pandas)
+    * [Pyramid](#pyramid)
+    * [Tornado](#tornado)
 * [QML](#qml)
 * [R](#r)
 * [Racket](#racket)
@@ -179,14 +179,14 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Raspberry Pi](#raspberry-pi)
 * [REBOL](#rebol)
 * [Ruby](#ruby)
-  * [RSpec](#rspec)
-  * [Ruby on Rails](#ruby-on-rails)
-  * [Sinatra](#sinatra)
+    * [RSpec](#rspec)
+    * [Ruby on Rails](#ruby-on-rails)
+    * [Sinatra](#sinatra)
 * [Rust](#rust)
 * [Sage](#sage)
 * [Scala](#scala)
-  * [Lift](#lift)
-  * [Play Scala](#play-scala)
+    * [Lift](#lift)
+    * [Play Scala](#play-scala)
 * [Scheme](#scheme)
 * [Scilab](#scilab)
 * [Scratch](#scratch)
@@ -201,15 +201,15 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [SQL Server](#sql-server)
 * [Standard ML](#standard-ml)
 * [Swift](#swift)
-  * [Vapor](#vapor)
+    * [Vapor](#vapor)
 * [Tcl](#tcl)
 * [TEI](#tei)
 * [Teradata](#teradata)
 * [Tizen](#tizen)
 * [TLA](#tla)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
-  * [Deno](#deno)
+    * [Angular](#angular)
+    * [Deno](#deno)
 * [Unix](#unix)
 * [V](#v)
 * [Verilog](#verilog)
@@ -1031,7 +1031,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [The Java Web Scraping Handbook](https://www.scrapingbee.com/java-webscraping-book) - Kevin Sahin (PDF, HTML)
 * [Think Data Structures: Algorithms and Information Retrieval in Java](https://greenteapress.com/wp/think-data-structures/) - Allen B. Downey (PDF, HTML)
 * [Think Java: How to Think Like a Computer Scientist, 2nd Edition](https://greenteapress.com/wp/think-java-2e/) - Allen B. Downey and Chris Mayfield (HTML, PDF) [(Interactive version by Trinket)](https://books.trinket.io/thinkjava2/)
-  * [Think Java: How to Think Like a Computer Scientist](https://greenteapress.com/wp/think-java/) - Allen B. Downey and Chris Mayfield (HTML, PDF) [(Interactive version by Trinket)](https://books.trinket.io/thinkjava/)
+    * [Think Java: How to Think Like a Computer Scientist](https://greenteapress.com/wp/think-java/) - Allen B. Downey and Chris Mayfield (HTML, PDF) [(Interactive version by Trinket)](https://books.trinket.io/thinkjava/)
 * [Using RxJava 2 Tutorial](https://www.vogella.com/tutorials/RxJava/article.html) - Lars Vogel, Simon Scholz (HTML)
 * [Welcome to Java for Python Programmers](https://runestone.academy/runestone/books/published/java4python/index.html) - Brad Miller
 * [Welcome to the Java Workshop (2006)](http://javaworkshop.sourceforge.net) - Trevor Miller
@@ -1295,9 +1295,9 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [React Succinctly](https://www.syncfusion.com/ebooks/react-succinctly) - Samer Buna
 * [React Tutorial](https://reactjs.org/tutorial/tutorial.html)
 * React Tutorial by Josh Finnie
-  * [Part 1](http://www.joshfinnie.com/blog/reactjs-tutorial-part-1/)
-  * [Part 2](http://www.joshfinnie.com/blog/reactjs-tutorial-part-2/)
-  * [Part 3](http://www.joshfinnie.com/blog/reactjs-tutorial-part-3/)
+    * [React Tutorial - Part 1](http://www.joshfinnie.com/blog/reactjs-tutorial-part-1/)
+    * [React Tutorial - Part 2](http://www.joshfinnie.com/blog/reactjs-tutorial-part-2/)
+    * [React Tutorial - Part 3](http://www.joshfinnie.com/blog/reactjs-tutorial-part-3/)
 * [React with ASP.NET Core Tutorial](https://reactjs.net/getting-started/aspnetcore.html)
 * [React.js Tutorial: Now is Your Time to Try It, Right in Your Browser](https://codegeekz.com/react-js-tutorial/)
 * [SurviveJS - Webpack and React](http://survivejs.com)
@@ -1830,14 +1830,14 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [A Whirlwind Tour of Python](http://www.oreilly.com/programming/free/files/a-whirlwind-tour-of-python.pdf) - Jake VanderPlas (PDF) [(EPUB, MOBI)](http://www.oreilly.com/programming/free/a-whirlwind-tour-of-python.csp?download=yes)
 * [Architecture Patterns with Python](https://www.cosmicpython.com/book/preface.html) - Harry J.W. Percival & Bob Gregory (HTML)
 * [Automate the Boring Stuff with Python, 2nd Edition: Practical Programming for Total Beginners](https://automatetheboringstuff.com/2e/chapter0/) - Al Sweigart (3.8)
-  * [Automate the Boring Stuff with Python: Practical Programming for Total Beginners](https://automatetheboringstuff.com/chapter0/) - Al Sweigart (3.4)
+    * [Automate the Boring Stuff with Python: Practical Programming for Total Beginners](https://automatetheboringstuff.com/chapter0/) - Al Sweigart (3.4)
 * [Beej's Guide to Python Programming - For Beginners](http://beej.us/guide/bgpython/) - Brian "Beej Jorgensen" Hall (HTML,PDF)
 * [Beyond the Basic Stuff with Python](https://inventwithpython.com/beyond/) - Al Sweigart (3.x)
 * [Biopython Tutorial and Cookbook](https://biopython.org/DIST/docs/tutorial/Tutorial.pdf) (PDF)
 * [Build applications in Python the antitextbook](http://github.com/thewhitetulip/build-app-with-python-antitextbook) (3.x) (HTML, PDF, EPUB, Mobi)
 * [Building Skills in Object-Oriented Design, V4](https://slott56.github.io/building-skills-oo-design-book/build/html/) - Steven F. Lott (3.7)
-  * [Building Skills in Object-Oriented Design, Release 2.2.1](https://web.archive.org/web/20150824204101/http://buildingskills.itmaybeahack.com/book/oodesign-python-2.2/latex/BuildingSkillsinOODesign.pdf) - Steven F. Lott (PDF) (2.2.1)
-  * [Building Skills in Object-Oriented Design, Release 3.1](https://web.archive.org/web/20160322093622/http://buildingskills.itmaybeahack.com/book/oodesign-3.1/latex/BuildingSkillsinObject-OrientedDesign.pdf) - Steven F. Lott (PDF) (3.1)
+    * [Building Skills in Object-Oriented Design, Release 2.2.1](https://web.archive.org/web/20150824204101/http://buildingskills.itmaybeahack.com/book/oodesign-python-2.2/latex/BuildingSkillsinOODesign.pdf) - Steven F. Lott (PDF) (2.2.1)
+    * [Building Skills in Object-Oriented Design, Release 3.1](https://web.archive.org/web/20160322093622/http://buildingskills.itmaybeahack.com/book/oodesign-3.1/latex/BuildingSkillsinObject-OrientedDesign.pdf) - Steven F. Lott (PDF) (3.1)
 * [Building Skills in Python](https://web.archive.org/web/20190918094202/http://www.itmaybeahack.com/book/python-2.6/latex/BuildingSkillsinPython.pdf) - Steven F. Lott (PDF) (2.6)
 * [Clean Architectures in Python](https://www.pycabook.com) - Leonardo Giordani (3.x)
 * [Code Like a Pythonista: Idiomatic Python](https://web.archive.org/web/20180411011411/http://python.net/~goodger/projects/pycon/2007/idiomatic/handout.html) - David Goodger
@@ -1846,7 +1846,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Cracking Codes with Python](https://inventwithpython.com/cracking/) - Al Sweigart (3.6)
 * [Data Structures and Algorithms in Python](https://web.archive.org/web/20161016153130/http://www.brpreiss.com/books/opus7/html/book.html) - B. R. Preiss (PDF)
 * [Dive into Python 3](https://diveintopython3.problemsolving.io) - Mark Pilgrim (3.0)
-  * [Dive into Python](https://linux.die.net/diveintopython/html/toc/index.html) - Mark Pilgrim (2.3)
+    * [Dive into Python](https://linux.die.net/diveintopython/html/toc/index.html) - Mark Pilgrim (2.3)
 * [From Python to NumPy](https://www.labri.fr/perso/nrougier/from-python-to-numpy/) - Nicolas P. Rougier (3.6)
 * [Full Stack Python](https://www.fullstackpython.com) - Matt Makai
 * [Functional Programming in Python](https://www.oreilly.com/ideas/functional-programming-in-python) - David Mertz
@@ -1859,13 +1859,13 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [How to Code in Python 3](https://assets.digitalocean.com/books/python/how-to-code-in-python.pdf) - Lisa Tagliaferri (PDF)
 * [How to Make Mistakes in Python](http://www.oreilly.com/programming/free/files/how-to-make-mistakes-in-python.pdf) - Mike Pirnat (PDF) (1st edition)
 * [How to Think Like a Computer Scientist: Learning with Python, Interactive Edition](https://runestone.academy/runestone/books/published/thinkcspy/index.html) - Brad Miller, David Ranum, Jeffrey Elkner, Peter Wentworth, Allen B. Downey, Chris Meyers, and Dario Mitchell (3.2)
-  * [How to Think Like a Computer Scientist: Learning with Python 1st Edition](https://greenteapress.com/wp/learning-with-python/) - Allen B. Downey, Jeff Elkner and Chris Meyers (2.4) (HTML, PDF)
-  * [How to Think Like a Computer Scientist: Learning with Python 2nd Edition](https://openbookproject.net/thinkcs/python/english2e/) - Jeffrey Elkner, Allen B. Downey, and Chris Meyers (Using Python 2.x)
-  * [How to Think Like a Computer Scientist: Learning with Python 3 (RLE)](https://openbookproject.net/thinkcs/python/english3e/) - Peter Wentworth, Jeffrey Elkner, Allen B. Downey, and Chris Meyers [(PDF)](https://www.ict.ru.ac.za/Resources/cspw/thinkcspy3/thinkcspy3.pdf)
+    * [How to Think Like a Computer Scientist: Learning with Python 1st Edition](https://greenteapress.com/wp/learning-with-python/) - Allen B. Downey, Jeff Elkner and Chris Meyers (2.4) (HTML, PDF)
+    * [How to Think Like a Computer Scientist: Learning with Python 2nd Edition](https://openbookproject.net/thinkcs/python/english2e/) - Jeffrey Elkner, Allen B. Downey, and Chris Meyers (Using Python 2.x)
+    * [How to Think Like a Computer Scientist: Learning with Python 3 (RLE)](https://openbookproject.net/thinkcs/python/english3e/) - Peter Wentworth, Jeffrey Elkner, Allen B. Downey, and Chris Meyers [(PDF)](https://www.ict.ru.ac.za/Resources/cspw/thinkcspy3/thinkcspy3.pdf)
 * [Inside The Python Virtual Machine](https://leanpub.com/insidethepythonvirtualmachine) - Obi Ike-Nwosu (HTML, PDF, EPUB, Kindle) *(Leanpub account or valid email requested)*
 * [Intermediate Python](https://book.pythontips.com/en/latest/) - Muhammad Yasoob Ullah Khalid (1st edition)
 * [Introduction to Programming with Python](http://opentechschool.github.io/python-beginners/en/) (3.3)
-  * [Introduction to Programming Using Python](http://python-ebook.blogspot.co.uk) - Cody Jackson (1st edition) (2.3)
+    * [Introduction to Programming Using Python](http://python-ebook.blogspot.co.uk) - Cody Jackson (1st edition) (2.3)
 * [Introduction to Python](http://kracekumar.com/post/71171551647/introduction-to-python) - Kracekumar (2.7.3)
 * [Introduction to Python for Econometrics, Statistics and Numerical Analysis](https://www.kevinsheppard.com/files/teaching/python/notes/python_introduction_2020.pdf) - Kevin Sheppard (PDF) (3.8)
 * [Invent Your Own Computer Games With Python](https://inventwithpython.com/invent4thed/) - Al Sweigart (3.4)
@@ -1882,7 +1882,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Natural Language Processing (NLP) with Python — Tutorial](https://medium.com/towards-artificial-intelligence/natural-language-processing-nlp-with-python-tutorial-for-beginners-1f54e610a1a0) (PDF)
 * [Natural Language Processing with Python](http://www.nltk.org/book/) (3.x)
 * [Non-Programmer's Tutorial for Python 3](https://en.wikibooks.org/wiki/Non-Programmer%27s_Tutorial_for_Python_3) - Wikibooks (3.3)
-  * [Non-Programmer's Tutorial for Python 2.6](https://en.wikibooks.org/wiki/Non-Programmer%27s_Tutorial_for_Python_2.6) - Wikibooks (2.6)
+    * [Non-Programmer's Tutorial for Python 2.6](https://en.wikibooks.org/wiki/Non-Programmer%27s_Tutorial_for_Python_2.6) - Wikibooks (2.6)
 * [Official NumPy Reference](https://numpy.org/doc/stable/numpy-ref.pdf) - The NumPy Community (PDF)
 * [Picking a Python Version: A Manifesto](https://www.oreilly.com/ideas/picking-a-python-version) - David Mertz
 * [Porting to Python 3: An In-Depth Guide](http://python3porting.com) (2.6 - 2.x & 3.1 - 3.x)
@@ -1909,7 +1909,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Python Koans](https://github.com/gregmalcolm/python_koans) (2.7 or 3.x)
 * [Python Machine Learning By Example](https://www.packtpub.com/free-ebooks/python-machine-learning-example) - Yuxi (Hayden) Liu (Packt account *required*)
 * [Python Module of the Week](https://pymotw.com/3/) (3.x)
-  * [Python Module of the Week](https://pymotw.com/2/) (2.x)
+    * [Python Module of the Week](https://pymotw.com/2/) (2.x)
 * [Python Notes for Professionals](http://goalkicker.com/PythonBook/) - Compiled from StackOverflow documentation (PDF)
 * [Python Practice Book](http://anandology.com/python-practice-book/index.html) (2.7.1)
 * [Python Practice Projects](http://pythonpracticeprojects.com)
@@ -1935,7 +1935,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Think Complexity](https://greenteapress.com/wp/think-complexity-2e/) - Allen B. Downey (2nd Edition) (PDF, HTML)
 * [Think DSP - Digital Signal Processing in Python](https://greenteapress.com/wp/think-dsp/) - Allen B. Downey (PDF, HTML)
 * [Think Python 2nd Edition](https://greenteapress.com/wp/think-python-2e/) - Allen B. Downey (3.x) (HTML, PDF)
-  * [Think Python First Edition](https://greenteapress.com/wp/think-python/) - Allen B. Downey (2.x) (HTML, PDF)
+    * [Think Python First Edition](https://greenteapress.com/wp/think-python/) - Allen B. Downey (2.x) (HTML, PDF)
 * [Tiny Python 3.6 Notebook](https://github.com/mattharrison/Tiny-Python-3.6-Notebook) - Matt Harrison (3.6)
 * [Tiny Python Projects](http://tinypythonprojects.com/Tiny_Python_Projects.pdf) - Ken Youens-Clark(PDF)
 * [Web2py: Complete Reference Manual, 6th Edition (pre-release)](http://web2py.com/book) (2.5 - 2.x)
diff --git a/books/free-programming-books-nl.md b/books/free-programming-books-nl.md
index 993a4c618..628aebaa4 100644
--- a/books/free-programming-books-nl.md
+++ b/books/free-programming-books-nl.md
@@ -5,7 +5,7 @@
 * [COBOL](#cobol)
 * [Java](#java)
 * [PHP](#php)
-  * [Symfony](#symfony)
+    * [Symfony](#symfony)
 * [Python](#python)
 * [Scratch](#scratch)
 
diff --git a/books/free-programming-books-pl.md b/books/free-programming-books-pl.md
index c832068f3..5102f800a 100644
--- a/books/free-programming-books-pl.md
+++ b/books/free-programming-books-pl.md
@@ -18,10 +18,10 @@
 * [MySQL](#mysql)
 * [Perl](#perl)
 * [PHP](#php)
-  * [Symfony](#symfony)
+    * [Symfony](#symfony)
 * [Prolog](#prolog)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 * [Ruby](#ruby)
 * [SQL](#sql)
 
diff --git a/books/free-programming-books-pt_BR.md b/books/free-programming-books-pt_BR.md
index da1bba842..abc73558a 100644
--- a/books/free-programming-books-pt_BR.md
+++ b/books/free-programming-books-pt_BR.md
@@ -1,9 +1,9 @@
 ### Index
 
 * [Agnósticos](#agnósticos)
-  * [IDE / Editores](#ide--editores)
-  * [Programação](#programação)
-  * [Sistemas Operacionais](#sistemas-operacionais)
+    * [IDE / Editores](#ide--editores)
+    * [Programação](#programação)
+    * [Sistemas Operacionais](#sistemas-operacionais)
 * [Android](#android)
 * [Arduino](#arduino)
 * [Assembly](#assembly)
@@ -13,9 +13,9 @@
 * [Dart](#dart)
 * [Docker](#docker)
 * [Engenharia de software](#engenharia-de-software)
-  * [Arquitetura de Software](#arquitetura-de-software)
-  * [Metodologias de Desenvolvimento de Software](#metodologias-de-desenvolvimento-de-software)
-  * [Outros](#outros)
+    * [Arquitetura de Software](#arquitetura-de-software)
+    * [Metodologias de Desenvolvimento de Software](#metodologias-de-desenvolvimento-de-software)
+    * [Outros](#outros)
 * [Fundamentos Matemáticos Computacionais](#fundamentos-matemáticos-computacionais)
 * [Git](#git)
 * [Go](#go)
@@ -23,18 +23,18 @@
 * [HTML / CSS](#html--css)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
-  * [Backbone.js](#backbonejs)
-  * [Ember.js](#emberjs)
-  * [Express.js](#expressjs)
-  * [Grunt](#grunt)
-  * [Gulp](#gulp)
-  * [jQuery](#jquery)
-  * [Knockout.js](#knockoutjs)
-  * [Meteor](#meteor)
-  * [Node.js](#nodejs)
-  * [React](#react)
-  * [Vue.js](#vuejs)
+    * [AngularJS](#angularjs)
+    * [Backbone.js](#backbonejs)
+    * [Ember.js](#emberjs)
+    * [Express.js](#expressjs)
+    * [Grunt](#grunt)
+    * [Gulp](#gulp)
+    * [jQuery](#jquery)
+    * [Knockout.js](#knockoutjs)
+    * [Meteor](#meteor)
+    * [Node.js](#nodejs)
+    * [React](#react)
+    * [Vue.js](#vuejs)
 * [Kubernetes](#kubernetes)
 * [LaTeX](#latex)
 * [LISP](#lisp)
@@ -42,13 +42,13 @@
 * [Pascal](#pascal)
 * [PHP](#php)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 * [R](#r)
 * [RegEx](#regex)
 * [Ruby](#ruby)
 * [Shell / Bash Script](#shell--bash)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 
 
 ### Agnósticos
diff --git a/books/free-programming-books-ro.md b/books/free-programming-books-ro.md
index 8a394e174..3360fcd28 100644
--- a/books/free-programming-books-ro.md
+++ b/books/free-programming-books-ro.md
@@ -5,7 +5,7 @@
 * [HTML](#html)
 * [MySQL](#mysql)
 * [PHP](#php)
-  * [Symfony](#symfony)
+    * [Symfony](#symfony)
 * [Scratch](#scratch)
 
 
diff --git a/books/free-programming-books-ru.md b/books/free-programming-books-ru.md
index 9bcbf06d2..8292d7265 100644
--- a/books/free-programming-books-ru.md
+++ b/books/free-programming-books-ru.md
@@ -1,11 +1,11 @@
 ### Index
 
 * [0 - Language Agnostic](#0---language-agnostic)
-  * [Облачные Вычисления](#Облачные-вычисления)
-  * [Парадигмы Программирования](#Парадигмы-программирования)
-  * [Работа c cетью](#Работа-с-сетью)
-  * [Управление конфигурациями](#Управление-конфигурациями)
-  * [Экосистема открытого исходного кода](#open-source-ecosystem)
+    * [Облачные Вычисления](#Облачные-вычисления)
+    * [Парадигмы Программирования](#Парадигмы-программирования)
+    * [Работа c cетью](#Работа-с-сетью)
+    * [Управление конфигурациями](#Управление-конфигурациями)
+    * [Экосистема открытого исходного кода](#open-source-ecosystem)
 * [Assembly](#assembly)
 * [Bash](#bash)
 * [C](#c)
@@ -20,23 +20,23 @@
 * [Go](#go)
 * [Haskell](#haskell)
 * [HTML / CSS](#html--css)
-  * [Bootstrap](#bootstrap)
+    * [Bootstrap](#bootstrap)
 * [Java](#java)
-  * [Android](#android)
-  * [EasyMock](#easymock)
-  * [Hibernate](#hibernate)
-  * [JDBC](#jdbc)
-  * [JUnit](#junit)
-  * [Maven](#maven)
-  * [Spring](#spring)
-  * [Swing UI](#swing-ui)
+    * [Android](#android)
+    * [EasyMock](#easymock)
+    * [Hibernate](#hibernate)
+    * [JDBC](#jdbc)
+    * [JUnit](#junit)
+    * [Maven](#maven)
+    * [Spring](#spring)
+    * [Swing UI](#swing-ui)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
-  * [jQuery](#jquery)
-  * [Node.js](#nodejs)
-  * [nuxt.js](#nuxtjs)
-  * [React](#react)
-  * [vue.js](#vuejs)
+    * [AngularJS](#angularjs)
+    * [jQuery](#jquery)
+    * [Node.js](#nodejs)
+    * [nuxt.js](#nuxtjs)
+    * [React](#react)
+    * [vue.js](#vuejs)
 * [Kotlin](#kotlin)
 * [LaTeX](#latex)
 * [Lisp](#lisp)
@@ -46,30 +46,30 @@
 * [Objective-C](#objective-c)
 * [Perl](#perl)
 * [PHP](#php)
-  * [CakePHP](#cakephp)
-  * [CodeIgniter](#codeigniter)
-  * [Laravel](#laravel)
-  * [Symfony](#symfony)
+    * [CakePHP](#cakephp)
+    * [CodeIgniter](#codeigniter)
+    * [Laravel](#laravel)
+    * [Symfony](#symfony)
 * [Python](#python)
-  * [Django](#django)
-  * [Jupyter Notebook](#jupyter-notebook)
-  * [NumPy](#numpy)
-  * [Pycharm](#pycharm)
+    * [Django](#django)
+    * [Jupyter Notebook](#jupyter-notebook)
+    * [NumPy](#numpy)
+    * [Pycharm](#pycharm)
 * [R](#r)
 * [Ruby](#ruby)
-  * [RSpec](#rspec)
-  * [Ruby on Rails](#ruby-on-rails)
+    * [RSpec](#rspec)
+    * [Ruby on Rails](#ruby-on-rails)
 * [Rust](#rust)
 * [Scala](#scala)
 * [Scilab](#scilab)
 * [Scratch](#scratch)
 * [Smalltalk](#smalltalk)
 * [SQL](#sql)
-  * [FirebirdSQL](#firebirdsql)
-  * [PostgreSQL](#postgresql)
+    * [FirebirdSQL](#firebirdsql)
+    * [PostgreSQL](#postgresql)
 * [Swift](#swift)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 * [Unix](#unix)
 * [Vim](#vim)
 
diff --git a/books/free-programming-books-sk.md b/books/free-programming-books-sk.md
index 791c82720..6e7c4e5dc 100644
--- a/books/free-programming-books-sk.md
+++ b/books/free-programming-books-sk.md
@@ -1,9 +1,9 @@
 ### Index
 
 * [Language Agnostic](#language-agnostic)
-  * [Právo](#pravo)
+    * [Právo](#pravo)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 
 
 ### Language Agnostic
diff --git a/books/free-programming-books-tr.md b/books/free-programming-books-tr.md
index 23853fdfa..a4065cb75 100644
--- a/books/free-programming-books-tr.md
+++ b/books/free-programming-books-tr.md
@@ -20,7 +20,7 @@
 * [.NET Framework](#net-framework)
 * [PHP](#php)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 * [R](#r)
 * [Ruby](#ruby)
 * [Rust](#rust)
diff --git a/books/free-programming-books-uk.md b/books/free-programming-books-uk.md
index ecd7b0e82..82b1c10fd 100644
--- a/books/free-programming-books-uk.md
+++ b/books/free-programming-books-uk.md
@@ -3,13 +3,13 @@
 * [ClosureScript](#clojurescript)
 * [Haskell](#haskell)
 * [HTML / CSS](#html--css)
-  * [Bootstrap](#bootstrap)
+    * [Bootstrap](#bootstrap)
 * [Java](#java)
 * [JavaScript](#javascript)
 * [Language Agnostic](#language-agnostic)
 * [PHP](#php)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 * [Ruby](#ruby)
 
 
diff --git a/books/free-programming-books-zh.md b/books/free-programming-books-zh.md
index 05d48a664..b0946f963 100644
--- a/books/free-programming-books-zh.md
+++ b/books/free-programming-books-zh.md
@@ -1,87 +1,87 @@
 ## Index
 
 * [语言无关](#语言无关)
-  * [版本控制](#版本控制)
-  * [编程艺术](#编程艺术)
-  * [编辑器](#编辑器)
-  * [编译原理](#编译原理)
-  * [操作系统](#操作系统)
-  * [程序员杂谈](#程序员杂谈)
-  * [大数据](#大数据)
-  * [分布式系统](#分布式系统)
-  * [管理和监控](#管理和监控)
-  * [函数式概念](#函数式概念)
-  * [计算机图形学](#计算机图形学)
-  * [其它](#其它)
-  * [软件开发方法](#软件开发方法)
-  * [设计模式](#设计模式)
-  * [数据库](#数据库)
-  * [项目相关](#项目相关)
-  * [在线教育](#在线教育)
-  * [正则表达式](#正则表达式)
-  * [智能系统](#智能系统)
-  * [IDE](#ide)
-  * [Web](#web)
-  * [WEB服务器](#web服务器)
+    * [版本控制](#版本控制)
+    * [编程艺术](#编程艺术)
+    * [编辑器](#编辑器)
+    * [编译原理](#编译原理)
+    * [操作系统](#操作系统)
+    * [程序员杂谈](#程序员杂谈)
+    * [大数据](#大数据)
+    * [分布式系统](#分布式系统)
+    * [管理和监控](#管理和监控)
+    * [函数式概念](#函数式概念)
+    * [计算机图形学](#计算机图形学)
+    * [其它](#其它)
+    * [软件开发方法](#软件开发方法)
+    * [设计模式](#设计模式)
+    * [数据库](#数据库)
+    * [项目相关](#项目相关)
+    * [在线教育](#在线教育)
+    * [正则表达式](#正则表达式)
+    * [智能系统](#智能系统)
+    * [IDE](#ide)
+    * [Web](#web)
+    * [WEB服务器](#web服务器)
 * [语言相关](#语言相关)
-  * [Android](#android)
-  * [Assembly](#assembly)
-  * [AWK](#awk)
-  * [C](#c)
-  * [C#](#csharp)
-  * [C++](#cpp)
-  * [CoffeeScript](#coffeescript)
-  * [Dart](#dart)
-  * [Elasticsearch](#elasticsearch)
-  * [Elixir](#elixir)
-  * [Erlang](#erlang)
-  * [Fortran](#fortran)
-  * [Golang](#golang)
-  * [Haskell](#haskell)
-  * [HTML / CSS](#html--css)
-  * [HTTP](#http)
-  * [iOS](#ios)
-  * [Java](#java)
-  * [JavaScript](#javascript)
-    * [AngularJS](#angularjs)
-    * [Backbone.js](#backbonejs)
-    * [D3.js](#d3js)
-    * [Electron.js](#electronjs)
-    * [ExtJS](#extjs)
-    * [impress.js](#impressjs)
-    * [jQuery](#jquery)
-    * [Node.js](#nodejs)
-    * [React.js](#reactjs)
-    * [Vue.js](#vuejs)
-    * [Zepto.js](#zeptojs)
-  * [LaTeX](#latex)
-  * [LISP](#lisp)
-  * [Lua](#lua)
-  * [Markdown](#markdown)
-  * [MySQL](#mysql)
-  * [NoSQL](#nosql)
-  * [Perl](#perl)
-  * [PHP](#php)
-    * [Laravel](#laravel)
-    * [Symfony](#symfony)
-  * [PostgreSQL](#postgresql)
-  * [Python](#python)
-    * [Django](#django)
-  * [R](#r)
-  * [reStructuredText](#restructuredtext)
-  * [Ruby](#ruby)
-  * [Rust](#rust)
-  * [Scala](#scala)
-  * [Scheme](#scheme)
-  * [Scratch](#scratch)
-  * [Shell](#shell)
-  * [Swift](#swift)
-  * [TypeScript](#typescript)
-    * [Angular](#angular)
-    * [Deno](#deno)
-  * [VBA](#vba-microsoft-visual-basic-applications)
-  * [Vim](#vim)
-  * [Visual Prolog](#visual-prolog)
+    * [Android](#android)
+    * [Assembly](#assembly)
+    * [AWK](#awk)
+    * [C](#c)
+    * [C#](#csharp)
+    * [C++](#cpp)
+    * [CoffeeScript](#coffeescript)
+    * [Dart](#dart)
+    * [Elasticsearch](#elasticsearch)
+    * [Elixir](#elixir)
+    * [Erlang](#erlang)
+    * [Fortran](#fortran)
+    * [Golang](#golang)
+    * [Haskell](#haskell)
+    * [HTML / CSS](#html--css)
+    * [HTTP](#http)
+    * [iOS](#ios)
+    * [Java](#java)
+    * [JavaScript](#javascript)
+        * [AngularJS](#angularjs)
+        * [Backbone.js](#backbonejs)
+        * [D3.js](#d3js)
+        * [Electron.js](#electronjs)
+        * [ExtJS](#extjs)
+        * [impress.js](#impressjs)
+        * [jQuery](#jquery)
+        * [Node.js](#nodejs)
+        * [React.js](#reactjs)
+        * [Vue.js](#vuejs)
+        * [Zepto.js](#zeptojs)
+    * [LaTeX](#latex)
+    * [LISP](#lisp)
+    * [Lua](#lua)
+    * [Markdown](#markdown)
+    * [MySQL](#mysql)
+    * [NoSQL](#nosql)
+    * [Perl](#perl)
+    * [PHP](#php)
+        * [Laravel](#laravel)
+        * [Symfony](#symfony)
+    * [PostgreSQL](#postgresql)
+    * [Python](#python)
+        * [Django](#django)
+    * [R](#r)
+    * [reStructuredText](#restructuredtext)
+    * [Ruby](#ruby)
+    * [Rust](#rust)
+    * [Scala](#scala)
+    * [Scheme](#scheme)
+    * [Scratch](#scratch)
+    * [Shell](#shell)
+    * [Swift](#swift)
+    * [TypeScript](#typescript)
+        * [Angular](#angular)
+        * [Deno](#deno)
+    * [VBA](#vba-microsoft-visual-basic-applications)
+    * [Vim](#vim)
+    * [Visual Prolog](#visual-prolog)
 
 
 ## 语言无关
@@ -316,8 +316,8 @@
 ### Assembly
 
 * 逆向工程权威指南 《Reverse Engineering for Beginners》 - Dennis Yurichev, Antiy Labs, Archer
-  * [逆向工程权威指南 《Reverse Engineering for Beginners》 Vol.1](https://beginners.re/RE4B-CN-vol1.pdf) - Dennis Yurichev, Antiy Labs, Archer (PDF)
-  * [逆向工程权威指南 《Reverse Engineering for Beginners》 Vol.2](https://beginners.re/RE4B-CN-vol2.pdf) - Dennis Yurichev, Antiy Labs, Archer (PDF)
+    * [逆向工程权威指南 《Reverse Engineering for Beginners》 Vol.1](https://beginners.re/RE4B-CN-vol1.pdf) - Dennis Yurichev, Antiy Labs, Archer (PDF)
+    * [逆向工程权威指南 《Reverse Engineering for Beginners》 Vol.2](https://beginners.re/RE4B-CN-vol2.pdf) - Dennis Yurichev, Antiy Labs, Archer (PDF)
 * [C/C++面向WebAssembly编程](https://github.com/3dgen/cppwasm-book/tree/master/zh) - Ending, Chai Shushan (HTML, [:package: examples](https://github.com/3dgen/cppwasm-book/tree/master/examples))
 
 
diff --git a/casts/free-podcasts-screencasts-pt_BR.md b/casts/free-podcasts-screencasts-pt_BR.md
index 7a367588a..d4bf8129b 100644
--- a/casts/free-podcasts-screencasts-pt_BR.md
+++ b/casts/free-podcasts-screencasts-pt_BR.md
@@ -12,7 +12,7 @@
 * [PHP](#php)
 * [Python](#python)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 * [Vue.js](#vuejs)
 
 
diff --git a/casts/free-podcasts-screencasts-ru.md b/casts/free-podcasts-screencasts-ru.md
index 8cb45a656..d0a75fd97 100644
--- a/casts/free-podcasts-screencasts-ru.md
+++ b/casts/free-podcasts-screencasts-ru.md
@@ -8,7 +8,7 @@
 * [Gulp](#gulp)
 * [Haskell](#haskell)
 * [Java](#java)
-  * [Spring](#spring)
+    * [Spring](#spring)
 * [JavaScript](#javascript)
 * [.NET](#net)
 * [Node.js](#nodejs)
diff --git a/courses/free-courses-ar.md b/courses/free-courses-ar.md
index cf6ba91b1..136dbcba1 100644
--- a/courses/free-courses-ar.md
+++ b/courses/free-courses-ar.md
@@ -11,31 +11,31 @@
 * [Computer Architecture](#computer-architecture)
 * [Dart](#dart)
 * [Databases](#databases)
-  * [NoSQL](#nosql)
-  * [SQL](#sql)
+    * [NoSQL](#nosql)
+    * [SQL](#sql)
 * [Flutter](#flutter)
 * [Game Development](#game-development)
 * [Git](#git)
 * [HTML / CSS](#html--css)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [Gulp.js](#gulpjs)
-  * [jQuery](#jquery)
-  * [NodeJS](#nodejs)
-  * [PugJs](#pugjs)
-  * [React.js](#reactjs)
-  * [Vue.js](#vuejs)
+    * [Gulp.js](#gulpjs)
+    * [jQuery](#jquery)
+    * [NodeJS](#nodejs)
+    * [PugJs](#pugjs)
+    * [React.js](#reactjs)
+    * [Vue.js](#vuejs)
 * [.NET](#net)
 * [Operating Systems](#operating-systems)
 * [PHP](#php)
 * [Prolog](#prolog)
 * [Python](#python)
-  * [Django](#django)
-  * [Flask](#flask)
+    * [Django](#django)
+    * [Flask](#flask)
 * [R](#r)
 * [Software Architecture](#software-architecture)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 
 
 ### Algorithms & Data Structures
diff --git a/courses/free-courses-bn.md b/courses/free-courses-bn.md
index f38ddad38..406438e49 100644
--- a/courses/free-courses-bn.md
+++ b/courses/free-courses-bn.md
@@ -9,13 +9,13 @@
 * [Git](#git)
 * [Go](#go)
 * [HTML and CSS](#html-and-css)
-  * [Bootstrap](#bootstrap)
+    * [Bootstrap](#bootstrap)
 * [IDE and Editors](#ide-and-editors)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [jQuery](#jquery)
-  * [Node.js](#nodejs)
-  * [React](#react)
+    * [jQuery](#jquery)
+    * [Node.js](#nodejs)
+    * [React](#react)
 * [Kotlin](#kotlin)
 * [MySQL](#mysql)
 * [PHP](#php)
diff --git a/courses/free-courses-en.md b/courses/free-courses-en.md
index 8695c6940..f6721e3b0 100644
--- a/courses/free-courses-en.md
+++ b/courses/free-courses-en.md
@@ -20,8 +20,8 @@
 * [Dart](#dart)
 * [Data Science](#data-science)
 * [Databases](#databases)
-  * [NoSQL](#nosql)
-  * [SQL](#sql)
+    * [NoSQL](#nosql)
+    * [SQL](#sql)
 * [Deep Learning](#deep-learning)
 * [Docker](#docker)
 * [Flutter](#flutter)
@@ -33,17 +33,17 @@
 * [iOS](#ios)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
-  * [D3.js](#d3js)
-  * [Electron](#electron)
-  * [jQuery](#jquery)
-  * [Next.js](#nextjs)
-  * [NodeJS](#nodejs)
-  * [React](#react)
-  * [React Native](#react-native)
-  * [Redux](#redux)
-  * [Svelte](#svelte)
-  * [Vue.js](#vuejs)
+    * [AngularJS](#angularjs)
+    * [D3.js](#d3js)
+    * [Electron](#electron)
+    * [jQuery](#jquery)
+    * [Next.js](#nextjs)
+    * [NodeJS](#nodejs)
+    * [React](#react)
+    * [React Native](#react-native)
+    * [Redux](#redux)
+    * [Svelte](#svelte)
+    * [Vue.js](#vuejs)
 * [Kotlin](#kotlin)
 * [Kubernetes](#kubernetes)
 * [Linux](#linux)
@@ -62,8 +62,8 @@
 * [PLC - Programmable logic controllers](#plc---programmable-logic-controllers)
 * [Processing](#processing)
 * [Python](#python)
-  * [Django](#django)
-  * [Flask](#flask)
+    * [Django](#django)
+    * [Flask](#flask)
 * [QB64](#QB64)
 * [R](#r)
 * [Robotics](#robotics)
@@ -74,11 +74,11 @@
 * [Solidity](#solidity)
 * [Spark](#spark)
 * [Swift](#swift)
-  * [Vapor](#vapor)
+    * [Vapor](#vapor)
 * [Theory](#theory)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
-  * [Deno](#deno)
+    * [Angular](#angular)
+    * [Deno](#deno)
 * [Verilog / VHDL / SystemVerilog](#verilog--vhdl--systemverilog)
 * [Web Development](#web-development)
 
diff --git a/courses/free-courses-fa_IR.md b/courses/free-courses-fa_IR.md
index 6a61f083f..a2f59b024 100644
--- a/courses/free-courses-fa_IR.md
+++ b/courses/free-courses-fa_IR.md
@@ -5,18 +5,18 @@
 * [Git](#git)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [React](#react)
+    * [React](#react)
 * [Kotlin](#kotlin)
 * [Linux](#linux)
 * [Machine Learning](#machine-learning)
 * [Network](#network)
 * [PHP](#php)
-  * [Codeigniter](#codeigniter)
-  * [Laravel](#laravel)
-  * [Yii](#yii)
+    * [Codeigniter](#codeigniter)
+    * [Laravel](#laravel)
+    * [Yii](#yii)
 * [Python](#python)
-  * [Django](#django)
-  * [Flask](#flask)
+    * [Django](#django)
+    * [Flask](#flask)
 * [Web Development](#web-development)
 
 
diff --git a/courses/free-courses-fr.md b/courses/free-courses-fr.md
index 0768f24b4..95a9147ec 100644
--- a/courses/free-courses-fr.md
+++ b/courses/free-courses-fr.md
@@ -10,9 +10,9 @@
 * [HTML / CSS](#html--css)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [jQuery](#jquery)
-  * [React](#react)
-  * [Vue.js](#vuejs)
+    * [jQuery](#jquery)
+    * [React](#react)
+    * [Vue.js](#vuejs)
 * [Linux](#linux)
 * [PHP](#php)
 * [Python](#python)
diff --git a/courses/free-courses-hi.md b/courses/free-courses-hi.md
index c0c61aca3..e901b5415 100644
--- a/courses/free-courses-hi.md
+++ b/courses/free-courses-hi.md
@@ -10,16 +10,16 @@
 * [HTML and CSS](#html-and-css)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [Next.js](#nextjs)
-  * [React](#react)
+    * [Next.js](#nextjs)
+    * [React](#react)
 * [Machine Learning](#machine-learning)
 * [PHP](#php)
 * [Python](#python)
-  * [Django](#django)
-  * [Flask](#flask)
+    * [Django](#django)
+    * [Flask](#flask)
 * [R](#r)
 * [Ruby](#ruby)
-  * [Ruby on Rails](#ruby-on-rails)
+    * [Ruby on Rails](#ruby-on-rails)
 
 
 ### Algorithms
diff --git a/courses/free-courses-id.md b/courses/free-courses-id.md
index f03a8bbe2..39b2333b5 100644
--- a/courses/free-courses-id.md
+++ b/courses/free-courses-id.md
@@ -16,11 +16,11 @@
 * [Gradle](#gradle)
 * [HTML / CSS](#html--css)
 * [Java](#java)
-  * [Spring](#spring)
+    * [Spring](#spring)
 * [JavaScript](#javascript)
-  * [Node](#node)
-  * [React](#react)
-  * [Vue](#vue)
+    * [Node](#node)
+    * [React](#react)
+    * [Vue](#vue)
 * [Kotlin](#kotlin)
 * [Kubernetes](#kubernetes)
 * [Linux](#linux)
@@ -29,12 +29,12 @@
 * [MongoDB](#mongodb)
 * [MySQL](#mysql)
 * [PHP](#php)
-  * [Codeigniter](#codeigniter)
-  * [Laravel](#laravel)
+    * [Codeigniter](#codeigniter)
+    * [Laravel](#laravel)
 * [Python](#python)
-  * [Django](#django)
-  * [Flask](#flask)
-  * [PyTorch](#pytorch)
+    * [Django](#django)
+    * [Flask](#flask)
+    * [PyTorch](#pytorch)
 * [Redis](#redis)
 * [SASS / SCSS](#sass--scss)
 * [Solidity](#solidity)
diff --git a/courses/free-courses-it.md b/courses/free-courses-it.md
index ff64256f8..60fc291d4 100644
--- a/courses/free-courses-it.md
+++ b/courses/free-courses-it.md
@@ -8,11 +8,11 @@
 * [C#](#csharp)
 * [C++](#cpp)
 * [Database](#database)
-  * [SQL](#sql)
+    * [SQL](#sql)
 * [Delphi](#delphi)
 * [DevOps](#devops)
 * [Embedded](#embedded)
-  * [Arduino](#arduino)
+    * [Arduino](#arduino)
 * [Generale](#generale)
 * [Java](#java)
 * [JavaScript](#javascript)
@@ -26,12 +26,12 @@
 * [Ruby](#ruby)
 * [Sistemi Informativi](#sistemi-informativi)
 * [Sistemi Operativi](#sistemi-operativi)
-  * [Linux](#linux)
+    * [Linux](#linux)
 * [Strumenti di sviluppo](#strumenti-di-sviluppo)
-  * [Git](#git)
-  * [Maven](#maven)
+    * [Git](#git)
+    * [Maven](#maven)
 * [Web](#web)
-  * [Vue](#vue)
+    * [Vue](#vue)
 * [Workshop](#workshop)
 
 
diff --git a/courses/free-courses-ko.md b/courses/free-courses-ko.md
index 218cc888f..e51e97311 100644
--- a/courses/free-courses-ko.md
+++ b/courses/free-courses-ko.md
@@ -16,9 +16,9 @@
 * [iOS](#ios)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
-  * [Node.js](#node.js)
-  * [React.js](#react.js)
+    * [AngularJS](#angularjs)
+    * [Node.js](#node.js)
+    * [React.js](#react.js)
 * [Kotlin](#kotlin)
 * [Linux](#linux)
 * [Machine Learning](#machine-learning)
diff --git a/courses/free-courses-ml.md b/courses/free-courses-ml.md
index eddd1f635..0a6077016 100644
--- a/courses/free-courses-ml.md
+++ b/courses/free-courses-ml.md
@@ -4,7 +4,7 @@
 * [JavaScript](#javascript)
 * [PHP](#php)
 * [Python](#python)
-  * [Django](#django)
+    * [Django](#django)
 
 
 ### Android
diff --git a/courses/free-courses-pt_BR.md b/courses/free-courses-pt_BR.md
index 13265fc92..e65d52526 100644
--- a/courses/free-courses-pt_BR.md
+++ b/courses/free-courses-pt_BR.md
@@ -37,7 +37,7 @@
 * [Shell](#shell)
 * [Swift](#swift)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 * [Vue.js](#vuejs)
 * [WordPress](#wordpress)
 
diff --git a/courses/free-courses-ru.md b/courses/free-courses-ru.md
index f56db49e0..4e00bb278 100644
--- a/courses/free-courses-ru.md
+++ b/courses/free-courses-ru.md
@@ -10,8 +10,8 @@
 * [HTML](#html)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [Node.js](#nodejs)
-  * [React](#react)
+    * [Node.js](#nodejs)
+    * [React](#react)
 * [Julia](#julia)
 * [Kotlin](#kotlin)
 * [Perl](#perl)
diff --git a/courses/free-courses-si.md b/courses/free-courses-si.md
index f79f13fff..f0d4348da 100644
--- a/courses/free-courses-si.md
+++ b/courses/free-courses-si.md
@@ -4,7 +4,7 @@
 * [HTML / CSS](#html--css)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [React](#react)
+    * [React](#react)
 
 
 ### ASP.NET Core
@@ -30,4 +30,3 @@
 #### React
 
 * [Fundamentals \| React JS in Sinhala](https://youtube.com/playlist?list=PLvvtf05eMZ2DpDyWwmAjEuicvVxx4vIYB) - Fiqri Ismail (YouTube)
-
diff --git a/courses/free-courses-th.md b/courses/free-courses-th.md
index 16f0c3b35..874ca73a2 100644
--- a/courses/free-courses-th.md
+++ b/courses/free-courses-th.md
@@ -5,13 +5,13 @@
 * [C++](#cpp)
 * [Git](#git)
 * [JavaScript](#javascript)
-  * [NodeJS](#nodejs)
-  * [React](#react)
-  * [Vue.js](#vuejs)
+    * [NodeJS](#nodejs)
+    * [React](#react)
+    * [Vue.js](#vuejs)
 * [Python](#python)
 * [Ruby](#Ruby)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 
 
 ### C
diff --git a/courses/free-courses-vi.md b/courses/free-courses-vi.md
index b0a5abe14..8adba02de 100644
--- a/courses/free-courses-vi.md
+++ b/courses/free-courses-vi.md
@@ -14,8 +14,8 @@
 * [HTML](#html)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
-  * [jQuery](#jquery)
+    * [AngularJS](#angularjs)
+    * [jQuery](#jquery)
 * [Machine-Learning](#machine-learning)
 * [MongoDB](#mongodb)
 * [NodeJS](#nodejs)
@@ -28,7 +28,7 @@
 * [SQL](#sql)
 * [Swift](#swift)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 * [Unity](#unity)
 * [Vue](#vue)
 * [Wordpress](#wordpress)
diff --git a/more/free-programming-cheatsheets.md b/more/free-programming-cheatsheets.md
index d4e67eede..3311c9346 100644
--- a/more/free-programming-cheatsheets.md
+++ b/more/free-programming-cheatsheets.md
@@ -15,11 +15,11 @@
 * [IDE / Editors](#ide--editors)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [jQuery](#jquery)
-  * [Nest.js](#nestjs)
-  * [Nuxt.js](#nuxtjs)
-  * [React.js](#reactjs)
-  * [Vue.js](#vuejs)
+    * [jQuery](#jquery)
+    * [Nest.js](#nestjs)
+    * [Nuxt.js](#nuxtjs)
+    * [React.js](#reactjs)
+    * [Vue.js](#vuejs)
 * [Kotlin](#Kotlin)
 * [Kubernetes](#kubernetes)
 * [Language Translations](#language-translations)
@@ -112,8 +112,8 @@
 * [Git Cheat Sheet](https://education.github.com/git-cheat-sheet-education.pdf) - GitHub (PDF)
 * [Git Cheat Sheet](https://about.gitlab.com/images/press/git-cheat-sheet.pdf) - GitLab (PDF)
 * [Git Cheat Sheet](http://git.jk.gs) - Jan Krüger (PDF, SVG)
-  * [Git Cheat Sheet](https://jan-krueger.net/wordpress/wp-content/uploads/2007/09/git-cheat-sheet.pdf) (PDF)
-  * [Git Cheat Sheet - extended](https://jan-krueger.net/wordpress/wp-content/uploads/2007/09/git-cheat-sheet-v2.zip) (PDF)
+    * [Git Cheat Sheet](https://jan-krueger.net/wordpress/wp-content/uploads/2007/09/git-cheat-sheet.pdf) (PDF)
+    * [Git Cheat Sheet - extended](https://jan-krueger.net/wordpress/wp-content/uploads/2007/09/git-cheat-sheet-v2.zip) (PDF)
 * [Git Cheat Sheet](https://programmingwithmosh.com/wp-content/uploads/2020/09/Git-Cheat-Sheet.pdf) - Moshfegh Hamedani (PDF)
 * [Git ściąga (pl)](https://training.github.com/downloads/pl/github-git-cheat-sheet/) - GitHub
 * [GitHub Cheat Sheet](https://github.com/tiimgreen/github-cheat-sheet) - Tim Green (Markdown)
diff --git a/more/free-programming-interactive-tutorials-en.md b/more/free-programming-interactive-tutorials-en.md
index 00d41f12a..8bc3ff408 100644
--- a/more/free-programming-interactive-tutorials-en.md
+++ b/more/free-programming-interactive-tutorials-en.md
@@ -17,16 +17,16 @@
 * [Go](#go)
 * [Haskell](#haskell)
 * [HTML / CSS](#html--css)
-  * [Bootstrap](#bootstrap)
+    * [Bootstrap](#bootstrap)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
-  * [jQuery](#jquery)
-  * [React](#react)
-  * [Redux](#redux)
+    * [AngularJS](#angularjs)
+    * [jQuery](#jquery)
+    * [React](#react)
+    * [Redux](#redux)
 * [Kotlin](#kotlin)
 * [Language Agnostic](#language-agnostic)
-  * [Operating Systems](#operating-systems)
+    * [Operating Systems](#operating-systems)
 * [LaTeX](#latex)
 * [Lisp](#lisp)
 * [MATLAB](#matlab)
diff --git a/more/free-programming-interactive-tutorials-ja.md b/more/free-programming-interactive-tutorials-ja.md
index e026b8955..d6c78b61d 100644
--- a/more/free-programming-interactive-tutorials-ja.md
+++ b/more/free-programming-interactive-tutorials-ja.md
@@ -2,7 +2,7 @@
 
 * [HTML / CSS](#html--css)
 * [JavaScript](#javascript)
-  * [React](#react)
+    * [React](#react)
 * [Python](#python)
 
 
diff --git a/more/free-programming-playgrounds.md b/more/free-programming-playgrounds.md
index bedbf0bf3..119665f26 100644
--- a/more/free-programming-playgrounds.md
+++ b/more/free-programming-playgrounds.md
@@ -19,7 +19,7 @@
 * [Ionic](#ionic)
 * [Java](#java)
 * [JavaScript](#javascript)
-  * [AngularJS](#angularjs)
+    * [AngularJS](#angularjs)
 * [Kotlin](#kotlin)
 * [Kubernetes](#kubernetes)
 * [.Net](#dotnet)
@@ -43,7 +43,7 @@
 * [Svelte](#svelte)
 * [Swift](#swift)
 * [TypeScript](#typescript)
-  * [Angular](#angular)
+    * [Angular](#angular)
 * [V](#v)