diff --git a/Concurrent Systems/notes/7- MUTEX-free concurrency.md b/Concurrent Systems/notes/7- MUTEX-free concurrency.md
index 5aab377..23476c4 100644
--- a/Concurrent Systems/notes/7- MUTEX-free concurrency.md	
+++ b/Concurrent Systems/notes/7- MUTEX-free concurrency.md	
@@ -184,4 +184,6 @@ the implementation of the stack is non-blocking
 *Proof:*
 Let us consider an operation invocation performed by p
 - if it terminates, √
-- otherwise, TOP has changed between the first of TOP and the last Compare&set
\ No newline at end of file
+- otherwise, TOP has changed between the first of TOP and the last Compare&set
+	- but the only instruction that modifies TOP is the closing Compare&set
+		- which means that the invocation issued by another process has terminated! √
\ No newline at end of file