diff --git a/examples/ipsec-vpn-server/README.md b/examples/ipsec-vpn-server/README.md
index 766aab9..54e2222 100644
--- a/examples/ipsec-vpn-server/README.md
+++ b/examples/ipsec-vpn-server/README.md
@@ -1,6 +1,7 @@
 # References 
 
 - https://github.com/hwdsl2/docker-ipsec-vpn-server
+- https://blog.lrvt.de/dockerized-ikev2-vpn/
 
 # Notes