Add some internal links.

Doc/glossary.rst

@@ -27,7 +27,7 @@ Glossary
       :ref:`2to3-reference`.
 
    abstract base class
-      Abstract Base Classes (abbreviated ABCs) complement :term:`duck-typing` by
+      :ref:`abstract-base-classes` complement :term:`duck-typing` by
       providing a way to define interfaces when other techniques like
       :func:`hasattr` would be clumsy. Python comes with many built-in ABCs for
       data structures (in the :mod:`collections` module), numbers (in the

Doc/library/collections.rst

@@ -28,7 +28,7 @@ Python's general purpose built-in containers, :class:`dict`, :class:`list`,
 =====================   ====================================================================
 
 In addition to the concrete container classes, the collections module provides
-ABCs (abstract base classes) that can be used to test whether a class provides a
+:ref:`abstract-base-classes` that can be used to test whether a class provides a
 particular interface, for example, whether it is hashable or a mapping.
 
 .. seealso::
@@ -959,6 +959,7 @@ attribute.
    subclass) or an arbitrary sequence which can be converted into a string using
    the built-in :func:`str` function.
 
+.. _abstract-base-classes:
 
 ABCs - abstract base classes
 ----------------------------