diff --git a/Concurrent Systems/notes/11 - LTSs and Bisimulation.md b/Concurrent Systems/notes/11 - LTSs and Bisimulation.md
index 233a80e..67fd42d 100644
--- a/Concurrent Systems/notes/11 - LTSs and Bisimulation.md	
+++ b/Concurrent Systems/notes/11 - LTSs and Bisimulation.md	
@@ -67,3 +67,9 @@ However, p0 and q0 are not bisimilar: the transition q0 -> a -> q1 is not bisimu
 
 $S = \{(p0,q0), (p1,q1), (p2,q1), (p0,q2)\}$
 $S^{−1} = \{(q0,p0), (q1,p1), (q1,p2), (q2,p0)\}$
+
+>[!def] Theorem
+>Bisimilarity is an equivalence relation
+
+*Proof:*
+Reflexivity: we have to show that q ∼ q, for every q. Consider the following relation
\ No newline at end of file