title: Sphinx: cross-reference indexed item
body: <p>How can I cross-reference an indexed item inside a reStructuredText document?</p>
  
  <p>For example, how can I cross-reference SectionB:</p>
  
  <pre><code>.. index::
      pair: SectionA; SectionB
  
  SectionB
  --------
  
  SectionB description.
  </code></pre>
  
  <p>I tried using the index labels in references, such as:</p>
  
  <pre><code>:ref:`SectionB`
  </code></pre>
  
  <p>but this does not work.</p>