diff --git a/module2/03_nginx_ha/tasks.md b/module2/03_nginx_ha/tasks.md
index a3b5a52..da7b9d8 100644
--- a/module2/03_nginx_ha/tasks.md
+++ b/module2/03_nginx_ha/tasks.md
@@ -166,4 +166,5 @@ fi
 - https://nginx.org/ru/docs/http/ngx_http_upstream_module.html
 - https://ru.wikipedia.org/wiki/VRRP
 - https://keepalived.readthedocs.io/en/latest/
+- https://datatracker.ietf.org/doc/html/rfc2338
 - http://www.austintek.com/LVS/LVS-HOWTO/mini-HOWTO/LVS-mini-HOWTO.html
\ No newline at end of file