Cleanup (#3536)

free-programming-books.md

@@ -2294,7 +2294,6 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Exploratory Data Analysis with R](https://leanpub.com/exdata) - Roger D. Peng *(Leanpub account or valid email requested)*
 * [Introduction to Probability and Statistics Using R](https://github.com/gjkerns/IPSUR) - G. Jay Kerns (PDF)
 * [Learning Statistics with R](https://web.archive.org/web/20170625184412/http://health.adelaide.edu.au/psychology/ccs/teaching/lsr/) - Daniel Navarro
-* [Machine Learning with R](https://www.packtpub.com/packt/free-ebook/r-machine-learning) - Brett Lantz, Packt. (email address *requested*, not required)
 * [ModernDive](https://ismayc.github.io/moderndiver-book/) - Chester Ismay and Albert Y. Kim
 * [Practical Regression and Anova using R](http://cran.r-project.org/doc/contrib/Faraway-PRA.pdf) - Julian J. Faraway (PDF)
 * [R for Data Science](http://r4ds.had.co.nz) - Garrett Grolemund and Hadley Wickham
@@ -2314,14 +2313,13 @@ Kerridge (PDF) (email address *requested*, not required)
 
 ### Racket
 
-* [How to Design Programs 2e](http://www.ccs.neu.edu/home/matthias/HtDP2e/)
+* [How to Design Programs](https://htdp.org/2019-02-24/) - Matthias Felleisen, Robert Bruce Findler, Matthew Flatt, Shriram Krishnamurthi
 * [Programming Languages: Application and Interpretation](http://cs.brown.edu/courses/cs173/2012/book/index.html)
 * [The Racket Guide](http://docs.racket-lang.org/guide/index.html)
 
 
 ### Raspberry Pi
 
-* [Raspberry Pi Cookbook for Python Programmers](https://www.packtpub.com/packt/free-ebook/python-raspberry-pi-cookbook) - Tim Cox, Packt. (PDF) (email address *requested*, not required)
 * [Raspberry Pi: Measure, Record, Explore](https://leanpub.com/RPiMRE/read) - Malcolm Maclean (HTML)
 * [Raspberry Pi Users Guide - (2012)](http://www.cs.unca.edu/~bruce/Fall14/360/RPiUsersGuide.pdf) - Eben Upton (PDF)
 * [The Official Raspberry Pi Project Book](https://www.raspberrypi.org/magpi-issues/Projects_Book_v1.pdf) (PDF)
@@ -2343,7 +2341,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Learn Ruby First](https://essenceofchaos.gitbooks.io/learn-ruby-first/content/) - Frederick John
 * [Learn Ruby the Hard Way](http://learnrubythehardway.org/book/) - Zed Shaw
 * [Learn to Program](http://pine.fm/LearnToProgram/) - Chris Pine
-* [Mr. Neighborly's Humble Little Ruby Book](http://www.humblelittlerubybook.com)
+* [Mr. Neighborly's Humble Little Ruby Book](https://web.archive.org/web/20180321101922/http://www.humblelittlerubybook.com/book/html/index.html)
 * [Object Oriented Programming with Ruby](https://launchschool.com/books/oo_ruby) - Launch School
 * [Practicing Ruby](https://github.com/elm-city-craftworks/practicing-ruby-manuscripts)
 * [Programming Ruby](http://ruby-doc.com/docs/ProgrammingRuby/)
@@ -2439,7 +2437,7 @@ Kerridge (PDF) (email address *requested*, not required)
 
 * [Exploring Lift](http://exploring.liftweb.net) (published earlier as "The Definitive Guide to Lift", [PDF](http://groups.google.com/group/the-lift-book))
 * [Lift](https://github.com/tjweir/liftbook)
-* [Lift Cookbook](http://chimera.labs.oreilly.com/books/1234000000030/index.html) - Richard Dallaway
+* [Lift Cookbook](https://www.oreilly.com/library/view/lift-cookbook/9781449365042/) - Richard Dallaway
 * [Simply Lift](http://simply.liftweb.net/Simply_Lift.pdf) - David Pollak (PDF)
 
 
@@ -2454,7 +2452,6 @@ Kerridge (PDF) (email address *requested*, not required)
 * [A Pamphlet Against R. Computational Intelligence in Guile Scheme](https://panicz.github.io/pamphlet/)
 * [An Introduction to Scheme and its Implementation](http://www.cs.rpi.edu/academics/courses/fall00/ai/scheme/reference/schintro-v14/schintro_toc.html)
 * [Concrete Abstractions: An Introduction to Computer Science Using Scheme](https://gustavus.edu/+max/concrete-abstractions.html) - M. Hailperin, B. Kaiser, K. Knight
-* [How to Design Programs](http://htdp.org)
 * [Scheme Tutorial](http://www.cs.hut.fi/Studies/T-93.210/schemetutorial/)
 * [Simply Scheme: Introducing Computer Science](http://www.cs.berkeley.edu/~bh/ss-toc2.html) - B. Harvey, M. Wright
 * [Teach Yourself Scheme in Fixnum Days](https://ds26gte.github.io/tyscheme/index-Z-H-1.html)
@@ -2487,12 +2484,11 @@ Kerridge (PDF) (email address *requested*, not required)
 
 ### Smalltalk
 
-* [Deep into Pharo](http://books.pharo.org/deep-into-pharo/)
+* [Deep into Pharo](http://books.pharo.org/deep-into-pharo/) - Alexandre Bergel, Damien Cassou, Stéphane Ducasse, Jannik Laval
 * [Dynamic Web Development with Seaside](http://book.seaside.st/book/table-of-contents) -  S. Ducasse, L. Renggli, C. D. Shaffer, R. Zaccone
 * [Enterprise Pharo: a Web Perspective](http://books.pharo.org/enterprise-pharo/)
-* [Numerical Methods with Pharo](http://books.pharo.org/numerical-methods/)
-* [Pharo by Example](http://books.pharo.org/pharo-by-example/) (Smalltalk Implementation and IDE)
-* [Squeak By Example](http://www.squeakbyexample.org) (Smalltalk Implementation and IDE)
+* [Numerical Methods with Pharo](http://books.pharo.org/numerical-methods/) - Didier Besset, Stéphane Ducasse, Serge Stinckwich
+* [Pharo by Example](http://books.pharo.org/pharo-by-example/) - Andrew P. Black et al. (Smalltalk Implementation and IDE)
 * [Stef's Free Online Smalltalk Books](http://stephane.ducasse.free.fr/FreeBooks.html) (meta-list)
 
 
@@ -2515,7 +2511,7 @@ Kerridge (PDF) (email address *requested*, not required)
 
 ### SQL (implementation agnostic)
 
-* [Developing Time-Oriented Database Applications in SQL](http://www.cs.arizona.edu/people/rts/publications.html)
+* [Developing Time-Oriented Database Applications in SQL](https://www2.cs.arizona.edu/~rts/tdbbook.pdf) - Richard T. Snodgrass (PDF)
 * [SQL For Web Nerds](http://philip.greenspun.com/sql/)
 * [SQL Notes for Professionals](http://books.goalkicker.com/SQLBook/)
 * [Use The Index, Luke!: A Guide To SQL Database Performance](http://use-the-index-luke.com)