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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>
    <alltransclusions gatcontinue="DSS,_Support_of_Knowledge_Management" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1355" ns="10" title="Template:Case" />
      <page pageid="3257" ns="10" title="Template:CountryCaseLessonWgTemplate" />
      <page pageid="1371" ns="10" title="Template:DSS, Concrete application" />
      <page pageid="1375" ns="10" title="Template:DSS, DSS development" />
      <page pageid="1372" ns="10" title="Template:DSS, Decision support techniques used in the DSS" />
      <page pageid="1370" ns="10" title="Template:DSS, Description" />
      <page pageid="1376" ns="10" title="Template:DSS, Documentation" />
      <page pageid="1368" ns="10" title="Template:DSS, Name, responsible organisation and contact person" />
      <page pageid="3306" ns="10" title="Template:DSS, Non-wood forest products" />
      <page pageid="1369" ns="10" title="Template:DSS, Software identification" />
    </pages>
  </query>
</api>