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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-continue>
    <allfileusages gafcontinue="Hackers-and-innovation-epub-pdf-book111.png|7" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page" />
      <page pageid="2" ns="0" title="Introduction" />
      <page pageid="14" ns="0" title="Hacker Generations and Evolution" />
      <page pageid="25" ns="0" title="Hacker Innovation and Consumer Artefacts" />
      <page pageid="27" ns="0" title="Hacker Innovation Cycles" />
      <page pageid="36" ns="0" title="Product Innovations Designed to be Hacked" />
    </pages>
  </query>
</api>