adding infos in readme

README.md

@@ -27,6 +27,9 @@ then in another window launch the client, with two arguments :
 - **use of getpid** : https://www.includehelp.com/c/getpid-and-getppid-functions-in-c-linux.aspx
 - **use of signal** : https://linuxhint.com/signal_handlers_c_programming_language
 - **use of sigaction** : https://stackoverflow.com/a/17572787/9497573
+- **signal action on sleep** : https://unix.stackexchange.com/questions/351312/sigint-handler-runs-only-once
+- **signals are pending just on per type** : https://stackoverflow.com/questions/5285414/signal-queuing-in-c
+- **checking for pending signals** : https://www.gnu.org/software/libc/manual/html_node/Checking-for-Pending-Signals.html
 - **don't use pause** : https://www.gnu.org/software/libc/manual/html_node/Pause-Problems.html
 - **standard signal vs real time signals (with queue option)** : https://www.softprayog.in/programming/posix-real-time-signals-in-linux
 - **test time of functions in program** : https://stackoverflow.com/a/5833240/9497573