title: xpath: find a node that has a given attribute whose value contains a string
body: <p>Is there an xpath way to find a node that has a given attribute whose value contains a given string?</p>
  
  <p>For example I have an xml document and want to find a node where the <code>address</code> attribute contains the string <code>Downing</code>, so that I could find the following node:</p>
  
  <pre><code>&lt;person name="blair" address="10 Downing St. London"/&gt;
  </code></pre>