<!DOCTYPE book [
  <!ELEMENT book (section*) >
  <!ELEMENT section ANY >
  <!ATTLIST section id ID #REQUIRED >
  <!ELEMENT fn ANY >
  <!ATTLIST fn fnid ID #REQUIRED >
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<book>
  <section id='preface'>This book introduces XQuery...
    The examples are downloadable<fnref ref="fn1"/>...
  </section>
  <section id='context'>...</section>
  <section id='language'>...Expressions, introduced
   in <secRef refs='context'/>, are...
  </section>
  <section id='types'>...As described in
    <secRef refs='context language'/>, you can...
  </section>
  <fn fnid='fn1'>See http://datypic.com.</fn>
</book>
