Switch note to warning and add reference.

docs/resource-manager-api.rst

@@ -16,16 +16,18 @@ With this API, you can do the following:
     Don't forget to look at the :ref:`Authentication` section below.
     It's slightly different from the rest of this library.
 
-.. note::
+.. warning::
 
     Alpha
 
-    The projects.create() method is in the Alpha stage. It might be changed in
+    The `projects.create() API method`_ is in the Alpha stage. It might be changed in
     backward-incompatible ways and is not recommended for production use. It is
     not subject to any SLA or deprecation policy. Access to this feature is
     currently invite-only. For an invitation, contact our sales team at
     https://cloud.google.com/contact.
 
+.. _projects.create() API method: https://cloud.google.com/resource-manager/docs/creating-project
+
 Here's a quick example of the full life-cycle:
 
 .. code-block:: python