title: Linking external documentation in Sphinx
body: <p>I am trying to link from our project's extension documentation to the core documentation in Sphinx. I've  tried intersphinx, but from what I see it only supports objects, while our documentation doesn't refer to objects, it's just plain .rst.</p>
  <p>I've added</p>
  <pre class="lang-py prettyprint-override"><code>intersphinx_mapping = {
      'project': ('http://link-to-readthedocs/index.html', None),
  }
  </code></pre>
  <p>to conf.py and edited the link to <code>:ref:\`Documentation\` </code> and later <code>:doc:\`Documentation\` </code>. It didn't work.</p>
  <p>The question:</p>
  <p><strong>How to link from one projects' documentation to another in Sphinx for plain .rst files (not objects)?</strong></p>
  <p><strong>Edit</strong>: I've done <code>make html</code>, found my <code>objects.inv</code>, but now I guess I only have it locally? I'm not sure what I'm doing anymore, but when I try to check the <a href="https://stackoverflow.com/questions/30939867/how-to-properly-write-coss-references-to-external-documentation-with-intersphinx">object references</a>, I get:</p>
  <pre><code>UserWarning: intersphinx inventory 'http://myproject.com/index.html/objects.inv' not fetchable due to &lt;class 'urllib.error.HTTPError'&gt;: HTTP Error 404: Not Found
    '%s: %s' % (inv, err.__class__, err))
  </code></pre>