diff --git a/subjects/sudoku/audit/README.md b/subjects/sudoku/audit/README.md
index 5e7f42ba..bfbb53d5 100644
--- a/subjects/sudoku/audit/README.md
+++ b/subjects/sudoku/audit/README.md
@@ -231,3 +231,7 @@ Error
 ```
 
 ###### Does the program returns the value above?
+
+#### Bonus
+
+###### +Is the project using the Exact cover technique [Knuth's Algorithm X](https://en.wikipedia.org/wiki/Knuth%27s_Algorithm_X)