diff --git a/Concurrent Systems/notes/12 - CCS (che non so cosa voglia dire).md b/Concurrent Systems/notes/12 - CCS (che non so cosa voglia dire).md
index 994526c..01c5a98 100644
--- a/Concurrent Systems/notes/12 - CCS (che non so cosa voglia dire).md	
+++ b/Concurrent Systems/notes/12 - CCS (che non so cosa voglia dire).md	
@@ -19,9 +19,14 @@ The set of actions we shall consider is: $N \cup \bar{N} \cup \{\tau\}$
 It is also useful to force some processes of the system to synchronize between them (without the possibility of showing to the outside some actions)
 
 The restriction operator P\a restricts the scope of name a to process P (a is visible only from within P)
+https://en.wikipedia.org/wiki/Calculus_of_communicating_system
 
 This is similar to local variables in a procedure of an imperative program
 
+The set of CCS processes is defined by the following grammar:
+$$P::=\sum_{i \in I} \alpha _{i}.P_{i} \space |\space A(a_{1}\dots a
+_{n})\space|\space P|Q \space | P$$
+
 ![](images/Pasted%20image%2020250414103800.png)
 
 ![](images/Pasted%20image%2020250414104010.png)