+``webhelpers.markdown`` is a copy of Markdown 1.7, used as a fallback for
+``webhelpers.html.converters.markdown()`` if the full Markdown package is not
+installed. See the `Markdown <>` website for documentation on the Markdown
+format and this module. Markdown is now at version 2.x and contains new
+features and plugins which are too big to include in WebHelpers. There is also
+an alternate implementation called Markdown2. Both are available on PyPI. See
+the ``markdown()`` documentation for how to use them with WebHelpers.
+``webhelpers.textile`` is a copy of Textile, used by
+``webhelpers.html.converters.textilize()``. See the `Textile <>`_ site for
+documentation on the Textile format and this module.
+``webhelpers.string24`` is a copy of Python 2.4's ``string`` module, for
+programs still running on Python 2.3. It will be removed in a future version