Put implementation link into references.

pep-0382.txt

@@ -18,7 +18,7 @@ package across multiple directories on disk. In current Python
 versions, an algorithm to compute the packages __path__ must be
 formulated. With the enhancement proposed here, the import machinery
 itself will construct the list of directories that make up the
-package.
+package.   An implementation of this PEP is available at [1]_.
 
 Terminology
 ===========
@@ -194,6 +194,12 @@ mechanisms. extend_path will be adjusted to this specification;
 any other mechanism might cause portions to get added twice to
 __path__.
 
+References
+==========
+
+.. [1] PEP 382 branch
+       (http://hg.python.org/features/pep-382-2#pep-382)
+
 Copyright
 =========