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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.
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<?xml version="1.0"?>
<api>
  <query-continue>
    <alltransclusions gatcontinue="Biblio|3548" />
  </query-continue>
  <query>
    <pages>
      <page pageid="2971" ns="0" title="OED" />
      <page pageid="2972" ns="0" title="The Guardian Stylebook" />
      <page pageid="3474" ns="0" title="EndNote" />
      <page pageid="3498" ns="0" title="A Dictionary of Modern English Usage" />
      <page pageid="3503" ns="0" title="Fowler" />
      <page pageid="3543" ns="0" title="Pride and Prejudice" />
      <page pageid="3544" ns="0" title="The Times style and usage guide" />
      <page pageid="3545" ns="0" title="The Concise Oxford Dictionary of Literary Terms" />
      <page pageid="3546" ns="0" title="A history of the English language" />
      <page pageid="3547" ns="0" title="Broadcast English" />
    </pages>
  </query>
</api>