adding missing reference

weaverryan · weaverryan · commit 393e8d8bf47b · 2015-06-19T12:53:26.000-04:00
diff --git a/book/bundles.rst b/book/bundles.rst
@@ -171,3 +171,5 @@ As you move through the book, you'll learn how to persist objects to a database,
 create and validate forms, create translations for your application, write
 tests and much more. Each of these has their own place and role within the
 bundle.
+
+_`third-party bundles`: http://knpbundles.com
