diff --git a/README.md b/README.md
index 6db4ab245..88f710306 100644
--- a/README.md
+++ b/README.md
@@ -7,8 +7,8 @@ Developers mailing list: https://dev.eclipse.org/mailman/listinfo/wakaama-dev
 
     -+- core                   (the LWM2M engine)
      |    |
-     |    +- er-coap-13        (Slightly modified Erbium's CoAP engine from
-     |                          http://people.inf.ethz.ch/mkovatsc/erbium.php
+     |    +- er-coap-13        (Modified Erbium's CoAP engine from
+     |                          https://web.archive.org/web/20180316172739/http://people.inf.ethz.ch/mkovatsc/erbium.php)
      |
      +- tests                  (test cases)
      |