Added cross-references plus a note about dict & list shallow copying.
diff --git a/Doc/library/mutex.rst b/Doc/library/mutex.rst
index 523692f..151f0c1 100644
--- a/Doc/library/mutex.rst
+++ b/Doc/library/mutex.rst
@@ -8,8 +8,9 @@
The :mod:`mutex` module defines a class that allows mutual-exclusion via
-acquiring and releasing locks. It does not require (or imply) threading or
-multi-tasking, though it could be useful for those purposes.
+acquiring and releasing locks. It does not require (or imply)
+:mod:`threading` or multi-tasking, though it could be useful for those
+purposes.
The :mod:`mutex` module defines the following class: