The link for `` `designed`_ `` here doesn't work - I see what you meant to do, but this isn't how Sphinx documentation works (this generates a link to the ``rst`` file, and you want a link to another document that may or may not be an html file).  You'll want to get rid of the `` .. _designed: design.rst`` at the top of this file once you've fixed this, as well.

Fortunately, there's a better way to do this in sphinx (see http://sphinx-doc.org/markup/inline.html#cross-referencing-arbitrary-locations if you want more detail). Use the ``:ref:`` directive.  That is, change this to `` :ref:`designed` `` (or :ref:`models-design` if you take my comment in ``design.rst`` about changing the label name.) Note that this will replace the text with the section title, though, so what you probably want is actually something like `` :ref:`designed <models-design>` ``