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HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <pages>
      <page ns="0" title="API" missing="" />
      <page pageid="31711" ns="0" title="Main Page">
        <revisions>
          <rev user="Admin" timestamp="2012-01-23T09:19:55Z" comment="moved [[Main Page]] to [[Welcome to WICWiki your Christian Wiki]]" contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">#REDIRECT [[Welcome to WICWiki your Christian Wiki]]</rev>
        </revisions>
      </page>
    </pages>
  </query>
</api>