diff --git a/Concurrent Systems/notes/8 - Enhancing Liveness Properties.md b/Concurrent Systems/notes/8 - Enhancing Liveness Properties.md
index 4212bc1..d3a8f73 100644
--- a/Concurrent Systems/notes/8 - Enhancing Liveness Properties.md	
+++ b/Concurrent Systems/notes/8 - Enhancing Liveness Properties.md	
@@ -6,4 +6,6 @@ Can we take the most basic protocol that satisfies the most basic liveness prope
 
 **Enriched implementation:** when a process realizes that there is contention, it invokes need_help; when it completes its current operation, it invokes stop_help.
 
-Why is it different from lock/unlock? Because this allows failures, and they can also happen in the contention-free period.
\ No newline at end of file
+**Why is it different from lock/unlock?** Because this allows failures, and they can also happen in the contention-free period.
+
+PROBLEM: to distinguish a failure from a long delay, we need objects called ***failure detectors***, that provide processes information on the failed processes of the system. According to the type/quality of the info, several F.
\ No newline at end of file