diff --git a/async-message-resources.adoc b/async-message-resources.adoc
index ae1ad50..594705d 100644
--- a/async-message-resources.adoc
+++ b/async-message-resources.adoc
@@ -1,6 +1,8 @@
 # Async Message Resources
 
 #### The Protocol
+https://www.amqp.org/specification/0-9-1/amqp-org-download
+ <= AMQP Protocol 0.9.1 +
 http://docs.oasis-open.org/amqp/core/v1.0/amqp-core-complete-v1.0.pdf 
  <= AMQP Core Complete v1.0 (pdf) +