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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>
    <querypage name="Ancientpages">
      <results>
        <page value="20141118194401" timestamp="2014-11-18T19:44:01Z" ns="0" title="Working with JSTOR Data for Research" />
        <page value="20150130192741" timestamp="2015-01-30T19:27:41Z" ns="0" title="Curating Your Corpus for Better Analysis" />
        <page value="20150130194714" timestamp="2015-01-30T19:47:14Z" ns="0" title="Basic Troubleshooting" />
        <page value="20150203142337" timestamp="2015-02-03T14:23:37Z" ns="0" title="Getting Started" />
        <page value="20150212163408" timestamp="2015-02-12T16:34:08Z" ns="0" title="Getting Lots of Data: JSTOR Data for Research" />
        <page value="20150212163521" timestamp="2015-02-12T16:35:21Z" ns="0" title="Getting Lots of Data" />
        <page value="20160419162450" timestamp="2016-04-19T16:24:50Z" ns="0" title="Main Page" />
      </results>
    </querypage>
  </query>
</api>