diff --git a/index.html b/index.html
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@@ -144,6 +144,7 @@ <h2>Computer Systems Principles and Concurrent Programming</h2>
   <h2>Theory of Computing</h2>
   <br>
   <ul>
+    <li><b><a style="text-decoration:none" href="http://infolab.stanford.edu/~ullman/focs.html" target="_blank">Foundations of Computer Science</a></b></li>
     <li><b><a style="text-decoration:none" href="https://math.hws.edu/FoundationsOfComputation/" target="_blank">Foundations of Computation</a></b></li>
     <li><b><a style="text-decoration:none" href="http://www.theoryandapplications.org/" target="_blank">Automata, Computability and Complexity: Theory and Applications</a></b></li>
     <li><b><a style="text-decoration:none" href="https://introtcs.org/public/index.html" target="_blank">Introduction to Theoretical Computer Science</a></b></li>