diff --git a/books/free-programming-books-langs.md b/books/free-programming-books-langs.md
index d1327a785..d1b72bb94 100644
--- a/books/free-programming-books-langs.md
+++ b/books/free-programming-books-langs.md
@@ -351,7 +351,7 @@ Books on general-purpose programming that don't focus on a specific language are
 
 #### Non-X86
 
-* [Beginners Introduction to the Assembly Language of ATMEL-AVR-Microprocessors](http://www.avr-asm-download.de/beginner_en.pdf) - Gerhard Schmidt (PDF)
+* [Beginners Introduction to the Assembly Language of ATMEL-AVR-Microprocessors](https://kitsandparts.com/tutorials/assemblers/BeginnersAVRasm.pdf) - Gerhard Schmidt (PDF)
 * [Easy 6502](http://skilldrick.github.io/easy6502/) - Nick Morgan
 * [Machine Language for Beginners](https://archive.org/details/ataribooks-machine-language-for-beginners) - Richard Mansfield
 * [MIPS Assembly Language Programming Using QtSpim](http://www.egr.unlv.edu/~ed/MIPStextSMv11.pdf) - Ed Jorgensen (PDF)
@@ -395,7 +395,7 @@ Books on general-purpose programming that don't focus on a specific language are
 * [BashGuide](http://mywiki.wooledge.org/BashGuide) - Maarten Billemont (HTML) [(PDF)](http://s.ntnu.no/bashguide.pdf)
 * [Command line text processing with GNU Coreutils](https://learnbyexample.github.io/cli_text_processing_coreutils/) - Sundeep Agarwal
 * [Computing from the Command Line](https://learnbyexample.github.io/cli-computing/) - Sundeep Agarwal
-* [Conquer the Command Line](https://magpi.raspberrypi.org/books/command-line-second-edition/pdf/download) - Richard Smedley (PDF)
+* [Conquer the Command Line](https://www.mclibre.org/descargar/docs/revistas/magpi-books/the-magpi-essentials-bash-02-en-201902.pdf) - Richard Smedley (PDF)
 * [Conquering the Command Line](https://www.softcover.io/read/fc6c09de/unix_commands) - Mark Bates (HTML)
 * [Essential Bash](https://www.programming-books.io/essential/bash/) - Krzysztof Kowalczyk, StackOverflow Contributors
 * [Getting Started with BASH](http://www.hypexr.org/bash_tutorial.php) (HTML)
@@ -466,7 +466,7 @@ Books on general-purpose programming that don't focus on a specific language are
 * [Let us C](https://books.google.co.in/books?id=Ce6gAAAACAAJ&printsec=frontcover#v=onepage&q&f=false) - Yashavant Kanetkar (PDF)
 * [Modeling with Data](https://ben.klemens.org/pdfs/gsl_stats.pdf) - Ben Klemens (PDF)
 * [Modern C](https://gustedt.gitlabpages.inria.fr/modern-c/) - Jens Gustedt (PDF)
-* [Object-Oriented Programming With ANSI-C](http://www.planetpdf.com/codecuts/pdfs/ooc.pdf) (PDF)
+* [Object-Oriented Programming With ANSI-C](https://www.cs.rit.edu/~ats/books/ooc.pdf) - Axel-Tobias Schreiner (PDF)
 * [Programming in C](http://ee.hawaii.edu/~tep/EE160/Book/PDF/) - Bharat Kinariwala & Tep Dobry
 * [Programming in C](https://www.freetechbooks.com/programming-in-c-t1337.html) - Kishori Mundargi
 * [Structures and C](https://www.smashwords.com/books/view/644937) - Prakash Hegade