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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>
    <allcategories accontinue="Special_Forces_maps" />
  </query-continue>
  <query>
    <allcategories>
      <c size="4" pages="4" files="0" subcats="0" xml:space="preserve">10th Mountain Division maps</c>
      <c size="7" pages="7" files="0" subcats="0" xml:space="preserve">172nd Sep. Infantry BDE maps</c>
      <c size="8" pages="8" files="0" subcats="0" xml:space="preserve">2.8.5 maps</c>
      <c size="5" pages="5" files="0" subcats="0" xml:space="preserve">75th Ranger Regiment maps</c>
      <c size="2" pages="2" files="0" subcats="0" xml:space="preserve">82nd Airborne maps</c>
      <c size="8" pages="8" files="0" subcats="0" xml:space="preserve">AA3 maps</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Infantry Training maps</c>
      <c size="2" pages="2" files="0" subcats="0" xml:space="preserve">Pages with broken file links</c>
      <c size="2" pages="2" files="0" subcats="0" xml:space="preserve">Ranger School maps</c>
      <c size="4" pages="4" files="0" subcats="0" xml:space="preserve">SF Exclusive</c>
    </allcategories>
  </query>
</api>