diff --git a/books/free-programming-books-langs.md b/books/free-programming-books-langs.md
index bf3b8431e..2e1c05c6d 100644
--- a/books/free-programming-books-langs.md
+++ b/books/free-programming-books-langs.md
@@ -336,15 +336,15 @@ Books on general-purpose programming that don't focus on a specific language are
 * [ARM Assembly Language Programming](http://www.rigwit.co.uk/ARMBook/ARMBook.pdf) - Peter Knaggs (PDF) *( :construction: in process)*
 * [Assemblers And Loaders (1993)](http://www.davidsalomon.name/assem.advertis/asl.pdf) - David Salomon (PDF)
 * [Assembly Language Succinctly](https://www.syncfusion.com/succinctly-free-ebooks/assemblylanguage) - Christopher Rose, Syncfusion Inc. (HTML, PDF, EPUB, Kindle)
-* [PC Assembly Language](http://pacman128.github.io/pcasm/) - P. A. Carter
-* [Programming from the Ground Up](https://download-mirror.savannah.gnu.org/releases/pgubook/ProgrammingGroundUp-1-0-booksize.pdf) - Jonathan Bartlett (PDF)
+* [PC Assembly Language](http://pacman128.github.io/pcasm/) - P. A. Carter (CC BY-NC-SA)
+* [Programming from the Ground Up](https://download-mirror.savannah.gnu.org/releases/pgubook/ProgrammingGroundUp-1-0-booksize.pdf) - Jonathan Bartlett (PDF) (GFDL)
 * [Ralf Brown's Interrupt List](http://www.ctyme.com/rbrown.htm)
 * [Software optimization resources](http://www.agner.org/optimize/) - A. Fog
 * [The Art of Assembly Language (2003)](https://web.archive.org/web/20120525102637/http://maven.smith.edu/~thiebaut/ArtOfAssembly/artofasm.html) - Randall Hyde (PDF) *( :card_file_box: archived)*
 * [The Grain Docs](https://grain-lang.org/docs/)
 * [WebAssembly friendly programming with C/C++](https://github.com/3dgen/cppwasm-book/tree/master/en) - Ending, Chai Shushan, Yushih (HTML, [:package: examples](https://github.com/3dgen/cppwasm-book/tree/master/examples))
 * [Wizard Code, A View on Low-Level Programming](https://web.archive.org/web/20170712195930/http://vendu.twodots.nl/files/wizardcode4.pdf) - Tuomo Tuomo Venäläinen (PDF) *( :card_file_box: archived)*
-* [x86-64 Assembly Language Programming with Ubuntu](http://www.egr.unlv.edu/~ed/x86.html) - Ed Jorgensen (PDF)
+* [x86-64 Assembly Language Programming with Ubuntu](http://www.egr.unlv.edu/~ed/x86.html) - Ed Jorgensen (PDF) (CC BY-NC-SA)
 * [x86 Assembly](https://en.wikibooks.org/wiki/X86_Assembly) - Wikibooks
 * [x86 Disassembly](https://en.wikibooks.org/wiki/X86_Disassembly) - Wikibooks