diff --git a/.obsidian/workspace.json b/.obsidian/workspace.json
index aa2c3f5..c8ca628 100644
--- a/.obsidian/workspace.json
+++ b/.obsidian/workspace.json
@@ -213,9 +213,10 @@
   },
   "active": "cdcc59f1bf6d4ae1",
   "lastOpenFiles": [
-    "Pasted image 20250505083948.png",
+    "Pasted image 20250505084556.png",
     "Concurrent Systems/slides/class 15.pdf",
     "Concurrent Systems/notes/15 - A formal language for LTSs.md",
+    "Pasted image 20250505083948.png",
     "Pasted image 20250505083500.png",
     "Concurrent Systems/notes/14 Checking bisimilarity, an inference system.md",
     "Concurrent Systems/notes/12b - CCS cose varie.md",
@@ -236,7 +237,6 @@
     "Concurrent Systems/notes/images/Pasted image 20250429092543.png",
     "Concurrent Systems/notes/images/Pasted image 20250429092305.png",
     "Concurrent Systems/notes/images/Pasted image 20250429092055.png",
-    "Concurrent Systems/notes/images/Pasted image 20250429091959.png",
     "Concurrent Systems/slides/class 12.pdf",
     "HCIW/slides/HCI in the car.pdf",
     "Concurrent Systems/slides/class 11.pdf",
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 151e6d4..d712010 100644
--- a/Concurrent Systems/notes/15 - A formal language for LTSs.md	
+++ b/Concurrent Systems/notes/15 - A formal language for LTSs.md	
@@ -16,4 +16,9 @@ The language generated by this grammar will be denoted by Form; every element of
 
 ![](../../Pasted%20image%2020250505083948.png)
 
-To simplify the proofs, we consider a more general form of conjunction: $\land_{i \in I, \phi i}$
\ No newline at end of file
+To simplify the proofs, we consider a more general form of conjunction: $$\land_{i \in I, \phi_{i}}$$
+where I is any indexing set (possibility, also infinite). Satisfiability for this operator is similar to that for the binary operator.
+
+Of course, we can use the boolean constant FALSE (FF) and classical logical operators like disjunction $\lor$ and implication $=>$ (they can all be derived in the usual way from $TT, \lnot, \land$).
+
+Another very useful logical operator is "box": let us define $\lnot \lozenge a p$ 
\ No newline at end of file
diff --git a/Pasted image 20250505084556.png b/Pasted image 20250505084556.png
new file mode 100644
index 0000000..8ab6e7c
Binary files /dev/null and b/Pasted image 20250505084556.png differ