<?php version="1.0"?>
   <article>
     <artheader>
       <title>
         An Article
       </title>
       <author>
         <firstname>
           Sebastian
         </firstname>
         <surname>
           Bergmann
         </surname>
       </author>
     </artheader>

     <section id="foo">
       <title>
         Section One
       </title>
     </section>

     <section id="bar">
       <title>
         Section Two
       </title>

       <para>
         <xref linkend="foo" />
       </para>
     </section>
   </article>
