diff --git a/.gitignore b/.gitignore
index e10ba39e88c4a..1c19995a8e612 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,7 +8,7 @@
 *.orig
 *.tmp
 
-
+*.idea
 # #########################################################
 # Global/Diff.gitignore
 # #####################################
diff --git a/books/free-programming-books-en.md b/books/free-programming-books-en.md
index aa0faf46963a8..bbaf0b59ffe2a 100644
--- a/books/free-programming-books-en.md
+++ b/books/free-programming-books-en.md
@@ -5,6 +5,6 @@
 
 ### All
 
-* [English, By Programming Language](free-programming-books-langs.md)
-* [English, By Subject](free-programming-books-subjects.md)
+* [_English_, By Programming Language](free-programming-books-langs.md)
+* [_English_, By Subject](free-programming-books-subjects.md)
   (The list of books in English is here for historical reasons.)
diff --git a/books/free-programming-books-langs.md b/books/free-programming-books-langs.md
index 977fae7d59316..a21f5b0789a12 100644
--- a/books/free-programming-books-langs.md
+++ b/books/free-programming-books-langs.md
@@ -1989,7 +1989,7 @@ Books on general-purpose programming that don't focus on a specific language are
 * [Automate the Boring Stuff with Python, 3nd Edition: Practical Programming for Total Beginners](https://automatetheboringstuff.com/3e/) - Al Sweigart (HTML) (CC BY-NC-SA)
 * [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)
+* [Biopython Tutorial and Cookbook](https://biopython.org/wiki/Documentation) (HTML, PDF) 
 * [Build applications in Python the antitextbook](http://github.com/thewhitetulip/build-app-with-python-antitextbook) (3.x) (HTML, PDF, EPUB, Mobi)
 * [Building Data Products: The Ultimate Guide](https://resources.montecarlodata.com/c/ebook-building-data-products?x=gEwOdf) (HTML, EPUB)
 * [Building Skills in Object-Oriented Design, V4](https://slott56.github.io/building-skills-oo-design-book/build/html/) - Steven F. Lott (3.7)
@@ -2053,6 +2053,7 @@ Books on general-purpose programming that don't focus on a specific language are
 * [Porting to Python 3: An In-Depth Guide](http://python3porting.com) (2.6 - 2.x & 3.1 - 3.x)
 * [Practical Programming in Python](https://launchpadlibrarian.net/165489933/PracticalProgrammingPython2014.pdf) - Jeffrey Elkner (PDF)
 * [Practice Python Projects](https://learnbyexample.github.io/practice_python_projects/) - Sundeep Agarwal
+* [Principles of Data Science](https://openstax.org/details/books/principles-data-science) - OpenStax (Web, PDF) (CC BY-NC-SA 4.0)
 * [Pro Python Advanced coding techniques and tools](https://archive.org/download/python-books/Apress.Pro.Python.Advanced.Coding.Techniques.And.Tools.Jun.2010.ISBN.1430227575.pdf) - Marty Alchin (PDF)
 * [Problem Solving with Algorithms and Data Structures using Python](https://runestone.academy/runestone/books/published/pythonds3/index.html) - Bradley N. Miller, David L. Ranum (3.x)
 * [Program Arcade Games With Python And Pygame](http://programarcadegames.com) (3.3)