Adde

Author: margaret-hu

books/free-programming-books-subjects.md

@@ -254,6 +254,7 @@ Books that cover a specific programming language can be found in the [BY PROGRAM
 * [Computer Science I](https://cse.unl.edu/~cbourke/ComputerScienceOne.pdf) - Chris Bourke (PDF) (CC BY-SA)
 * [Computer Science II](https://cse.unl.edu/~cbourke/ComputerScienceTwo.pdf) - Chris Bourke (PDF) (CC BY-SA)
 * [CS Principles: Big Ideas in Programming](https://www.openbookproject.net/books/StudentCSP/) - Mark Guzdial, Barbara Ericson (HTML)
+* [Foundations of Computer Science](http://i.stanford.edu/~ullman/focs.html) - Alfred V. Aho, Jeffrey D. Ullman (PDF)
 * [Introduction to Computer Science](https://openstax.org/details/books/introduction-computer-science) - Jean Claude Franchitti et al. (PDF, HTML) (CC BY)
 * [Pull Requests and Code Review](https://scs.tl/book-pr) – Sebastien Castiel
 * [What to Look for in a Code Review](https://leanpub.com/whattolookforinacodereview) - Trisha Gee (HTML, PDF, EPUB, Kindle) *(Leanpub account or valid email requested)*