diff --git a/.obsidian/workspace.json b/.obsidian/workspace.json
index bec7fe3..b39b803 100644
--- a/.obsidian/workspace.json
+++ b/.obsidian/workspace.json
@@ -53,7 +53,7 @@
                 "file": "Concurrent Systems/slides/class 7.pdf",
                 "page": 5,
                 "left": -23,
-                "top": 593,
+                "top": 149,
                 "zoom": 0.680522565320665
               },
               "icon": "lucide-file-text",
@@ -237,6 +237,7 @@
   "lastOpenFiles": [
     "Concurrent Systems/slides/class 7.pdf",
     "Concurrent Systems/notes/7- MUTEX-free concurrency.md",
+    "Pasted image 20250324091452.png",
     "Concurrent Systems/notes/Pasted image 20250324082534.png",
     "Concurrent Systems/notes/6a - Alternatives to Atomicity.md",
     "Concurrent Systems/slides/class 6.pdf",
@@ -270,7 +271,6 @@
     "HCIW/notes/2 - Interface and Interaction for IoT.md",
     "HCIW/notes/3 - Beacons.md",
     "Concurrent Systems/notes/images/Pasted image 20250312121828.png",
-    "Concurrent Systems/notes/images/Pasted image 20250310172134.png",
     "Concurrent Systems/notes/1 - CS Basics2.md",
     "HCIW/notes/1 - UX for IoT.md",
     "HCIW/exercises/Exercise.md",
diff --git a/Concurrent Systems/notes/7- MUTEX-free concurrency.md b/Concurrent Systems/notes/7- MUTEX-free concurrency.md
index 8749839..3eafc60 100644
--- a/Concurrent Systems/notes/7- MUTEX-free concurrency.md	
+++ b/Concurrent Systems/notes/7- MUTEX-free concurrency.md	
@@ -63,4 +63,11 @@ this implementation satisfies the three requirements for the splitter
 2. not all processes can obtain L
 	- let us consider the last process that writes into LAST (this is an atomic register, so this is meaningful)
 	- if the door is closed, it receives R and √
-3. let $p_i$ be the first process that receives S 
\ No newline at end of file
+3. let $p_i$ be the first process that receives $S \to LAST=i$ in its second if
+		![[Pasted image 20250324091452.png]]
+
+### An Obstruction-free Timestamp Generator
+A **timestamp generator** is a concurrent object that provides a single operation get_ts such that:
+1. (*validity*) not two invocations of get_ts return the same value
+2. (*consistency*) if one process terminates its invocation of get_ts before another one starts, the first receives a timestamp that is smaller than the one received by the second one
+3. (*obstruction freedom*) if run in isolation
diff --git a/Pasted image 20250324091452.png b/Pasted image 20250324091452.png
new file mode 100644
index 0000000..eb8ef84
Binary files /dev/null and b/Pasted image 20250324091452.png differ