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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>
    <allimages gaicontinue="3_EU.pdf" />
  </query-continue>
  <query>
    <pages>
      <page pageid="6573" ns="6" title="File:151585586 (2).jpg" />
      <page pageid="6365" ns="6" title="File:1 EU.pdf" />
      <page pageid="6366" ns="6" title="File:1 nonEU.pdf" />
      <page pageid="6960" ns="6" title="File:2.3 Analytical framework ecosystem services.pdf" />
      <page pageid="6367" ns="6" title="File:2 EU.pdf" />
      <page pageid="6368" ns="6" title="File:2 nonEU.pdf" />
      <page pageid="6961" ns="6" title="File:3.1 Impacts of HyMo degradation on ecology 0.pdf" />
      <page pageid="6962" ns="6" title="File:3.2 Biological responses to degraded HyMo and multiple stress.pdf" />
      <page pageid="6963" ns="6" title="File:3.3 Evaluation of candidate hydromorphology indicators.pdf" />
      <page pageid="6964" ns="6" title="File:3.4 Guidance to detect impact of HyMo degradation on riparian ecosystems.pdf" />
    </pages>
  </query>
</api>