diff --git a/.obsidian/workspace.json b/.obsidian/workspace.json
index a9bcaab..b4e3dae 100644
--- a/.obsidian/workspace.json
+++ b/.obsidian/workspace.json
@@ -213,6 +213,7 @@
   },
   "active": "cdcc59f1bf6d4ae1",
   "lastOpenFiles": [
+    "Pasted image 20250505085454.png",
     "Concurrent Systems/slides/class 15.pdf",
     "Concurrent Systems/notes/15 - A formal language for LTSs.md",
     "Pasted image 20250505084741.png",
diff --git a/Concurrent Systems/notes/15 - A formal language for LTSs.md b/Concurrent Systems/notes/15 - A formal language for LTSs.md
index be6cb9e..0056d32 100644
--- a/Concurrent Systems/notes/15 - A formal language for LTSs.md	
+++ b/Concurrent Systems/notes/15 - A formal language for LTSs.md	
@@ -25,3 +25,10 @@ Another very useful logical operator is "box": let us define $\lnot \lozenge a p
 ![](../../Pasted%20image%2020250505084741.png)
 
 From the last condition, we have that $P $\models \square a \phi$ if and only if $$\forall P': P \xrightarrow{a} P' \implies P' \models \phi$$
+EXAMPLE: Let us now consider formula ☐aFF
+By definition, this happens only if, for every P’ resulting from P after action a, it holds P’ |= FF
+
+However, this can never happen, whatever P’ be;
+hence, P |= ☐aFF holds true only if P cannot perform any action a
+
+![](../../Pasted%20image%2020250505085454.png)
diff --git a/Pasted image 20250505085454.png b/Pasted image 20250505085454.png
new file mode 100644
index 0000000..09b6ce0
Binary files /dev/null and b/Pasted image 20250505085454.png differ