diff --git a/books/free-programming-books-subjects.md b/books/free-programming-books-subjects.md
index ed2630ddc..f8f821799 100644
--- a/books/free-programming-books-subjects.md
+++ b/books/free-programming-books-subjects.md
@@ -405,7 +405,7 @@ Books that cover a specific programming language can be found in the [BY PROGRAM
 ### Machine Learning
 
 * [A Brief Introduction to Machine Learning for Engineers](https://arxiv.org/pdf/1709.02840.pdf) - Osvaldo Simeone (PDF)
-* [A Brief Introduction to Neural Networks](https://www.dkriesel.com/en/science/neural_networks)
+* [A Brief Introduction to Neural Networks](https://www.dkriesel.com/en/science/neural_networks) (CC BY-ND)
 * [A Comprehensive Guide to Machine Learning](https://www.eecs189.org/static/resources/comprehensive-guide.pdf) - Soroush Nasiriany, Garrett Thomas, William Wang, Alex Yang (PDF)
 * [A Course in Machine Learning](http://ciml.info/dl/v0_9/ciml-v0_9-all.pdf) (PDF)
 * [A First Encounter with Machine Learning](https://web.archive.org/web/20210420163002/https://www.ics.uci.edu/~welling/teaching/ICS273Afall11/IntroMLBook.pdf) - Max Welling (PDF) *(:card_file_box: archived)*
@@ -420,11 +420,11 @@ Books that cover a specific programming language can be found in the [BY PROGRAM
 * [Dive into Deep Learning](https://d2l.ai)
 * [Explorations in Parallel Distributed Processing: A Handbook of Models, Programs, and Exercises](https://web.stanford.edu/group/pdplab/pdphandbook) - James L. McClelland
 * [Foundations of Machine Learning, Second Edition](https://mitpress.ublish.com/ebook/foundations-of-machine-learning--2-preview/7093/Cover) - Mehryar Mohri, Afshin Rostamizadeh, Ameet Talwalkar
-* [Free and Open Machine Learning](https://nocomplexity.com/documents/fossml/) - Maikel Mardjan (HTML)
+* [Free and Open Machine Learning](https://nocomplexity.com/documents/fossml/) - Maikel Mardjan (HTML) (CC BY-SA)
 * [Gaussian Processes for Machine Learning](https://www.gaussianprocess.org/gpml/) - Carl Edward Rasmussen, Christopher K.I. Williams
 * [IBM Machine Learning for Dummies](https://www.ibm.com/downloads/cas/GB8ZMQZ3) - Judith Hurwitz, Daniel Kirsch
 * [Information Theory, Inference, and Learning Algorithms](http://www.inference.phy.cam.ac.uk/itila/) - David J.C. MacKay
-* [Interpretable Machine Learning](https://christophm.github.io/interpretable-ml-book/) - Christoph Molnar
+* [Interpretable Machine Learning](https://christophm.github.io/interpretable-ml-book/) (CC BY-NC-SA) - Christoph Molnar
 * [Introduction to CNTK Succinctly](https://www.syncfusion.com/ebooks/cntk_succinctly) - James McCaffrey
 * [Introduction to Machine Learning](https://arxiv.org/abs/0904.3664v1) - Amnon Shashua
 * [Keras Succinctly](https://www.syncfusion.com/ebooks/keras-succinctly) - James McCaffrey