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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>
    <allfileusages gafcontinue="Frontal_arousal_rhythm_(average)_eegpedia.png|38" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page" />
      <page pageid="3" ns="0" title="Beta rhythm" />
      <page pageid="28" ns="0" title="6 Hz spike-and-wave bursts (WHAM and FOLD)" />
      <page pageid="38" ns="0" title="Frontal arousal rhythm" />
      <page pageid="47" ns="0" title="Breach rhythm" />
      <page pageid="69" ns="0" title="Eye blink artifact" />
      <page pageid="75" ns="0" title="Breathing artifact" />
      <page pageid="81" ns="0" title="FIRDA (frontal intermittent rhythmic delta activity)" />
      <page pageid="101" ns="0" title="Childhood Absence Epilepsy" />
      <page pageid="104" ns="0" title="CSWS (Continuous spike and wave during slow wave sleep)" />
    </pages>
  </query>
</api>