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HTML is good for debugging, but probably is not suitable for your application.
See complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <allusers>
      <u userid="166" name="ZUOBriann" />
      <u userid="117" name="Zane4475" />
      <u userid="110" name="ZelmaMcke" />
      <u userid="26" name="¡Hola! ¿Qué tal?" />
    </allusers>
  </query>
</api>