diff --git a/tor/README.md b/tor/README.md
index 83f26ac..0f2b3c9 100644
--- a/tor/README.md
+++ b/tor/README.md
@@ -63,3 +63,5 @@ $ curl -x socks5h://127.0.0.1:9050 ifconfig.me
 ## references
 
 - https://www.torproject.org/projects/obfsproxy-debian-instructions.html.en
+
+[1]: https://www.torproject.org/