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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>
    <allpages apcontinue="R_Certification" />
  </query-continue>
  <query>
    <allpages>
      <p pageid="3" ns="0" title="Code Coverage Tool for R" />
      <p pageid="19" ns="0" title="Ddr2016" />
      <p pageid="12" ns="0" title="Distributed Computing Working Group" />
      <p pageid="20" ns="0" title="Distributed Computing Working Group Progress Report 2016" />
      <p pageid="11" ns="0" title="Initial Survey of API Usage" />
      <p pageid="1" ns="0" title="Main Page" />
      <p pageid="7" ns="0" title="Native API stats of R.h" />
      <p pageid="9" ns="0" title="Native API stats of Rinternals.h with USE R INTERNALS" />
      <p pageid="8" ns="0" title="Native API stats of Rinternals.h without USE R INTERNALS" />
      <p pageid="10" ns="0" title="Native API stats of all header files" />
    </allpages>
  </query>
</api>