Missing source links.
diff --git a/Doc/library/abc.rst b/Doc/library/abc.rst
index 0302eb5..9fadbd2 100644
--- a/Doc/library/abc.rst
+++ b/Doc/library/abc.rst
@@ -7,6 +7,10 @@
.. sectionauthor:: Georg Brandl
.. much of the content adapted from docstrings
+**Source code:** :source:`Lib/abc.py`
+
+--------------
+
This module provides the infrastructure for defining an :term:`abstract base
class` (ABCs) in Python, as outlined in :pep:`3119`; see the PEP for why this
was added to Python. (See also :pep:`3141` and the :mod:`numbers` module