title: Get distinct values within specific attributes
body: <p>I've got the following XML Code:</p>
  
  <pre><code>&lt;!-- language: xml --&gt;
  &lt;Stats&gt;
    &lt;Stat&gt;
      &lt;Data Name="Value"&gt;63.76&lt;/Data&gt;
      &lt;Data Name="Entity"&gt;first&lt;/Data&gt;
    &lt;/Stat&gt;
    &lt;Stat&gt;
      &lt;Data Name="Value"&gt;51.23&lt;/Data&gt;
      &lt;Data Name="Entity"&gt;second&lt;/Data&gt;
    &lt;/Stat&gt;
    &lt;Stat&gt;
      &lt;Data Name="Value"&gt;46.1&lt;/Data&gt;
      &lt;Data Name="Entity"&gt;third&lt;/Data&gt;
    &lt;/Stat&gt;
    &lt;Stat&gt;
      &lt;Data Name="Value"&gt;61.21&lt;/Data&gt;
      &lt;Data Name="Entity"&gt;first&lt;/Data&gt;
    &lt;/Stat&gt;
  &lt;/Stats&gt;
  </code></pre>
  
  <p>I want to filter only where 'Data[@Name='Entity']. Using xpath: <code>/Stats/Stat/Data[@Name="Entity"]</code> returns:
  first
  second
  third
  first</p>
  
  <p>But I want the results to be unique. So I only get:
  first
  second
  third</p>
  
  <p>EDIT: I need this to work for xpath version 1.0.</p>