diff --git a/README.md b/README.md
index 28f30e5..8f821cb 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,7 @@ A few example programs are provided in the `tests/` directory:
 * _Sudoku_ - https://en.wikipedia.org/wiki/Sudoku
   * _Samurai Sudoku_
 * _Sujiko_ - https://en.wikipedia.org/wiki/Sujiko
+* _xkcd_ - https://xkcd.com/287/
 * _Zebra puzzle (Einstein's riddle)_ - https://en.wikipedia.org/wiki/Zebra_Puzzle
 
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