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HTML is good for debugging, but is unsuitable for application use.
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To see the non HTML representation of the XML format, set format=xml.
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<?xml version="1.0"?>
<api>
  <query-continue>
    <allcategories accontinue="Constructores_de_Fórmula_1" />
  </query-continue>
  <query>
    <allcategories>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Automobiles Alpine</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Automóviles de las 24 Horas de Le Mans</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Automóviles ganadores de las 24 Horas de Le Mans</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Automóviles superdeportivos</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Boulogne-Billancourt</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Capitanes del Fútbol Club Barcelona</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Cars</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Casos de dopaje en fútbol</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Centrocampistas de fútbol</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Compañías y marcas comerciales epónimas</c>
    </allcategories>
  </query>
</api>