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

@@ -27,10 +27,9 @@ Python's general purpose built-in containers, :class:`dict`, :class:`list`,
 :class:`defaultdict`    dict subclass that calls a factory function to supply missing values  .. versionadded:: 2.5
 =====================   ====================================================================  ===========================
 
-In addition to containers, the collections module provides some ABCs
-(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.
+In addition to the concrete container classes, the collections module provides
+: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::