Query Result: Books with the first two authors

<bib>
  <book>
    <title>TCP/IP Illustrated</title>
    <author><last>Stevens</last><first>W.</first></author>
  </book>

  <book>
    <title>Advanced Programming in the Unix Environment</title>
    <author><last>Stevens</last><first>W.</first></author>
  </book>

  <book>
    <title>Data on the Web</title>
      <author><last>Abiteboul</last><first> Serge</first></author>
      <author><last>Buneman</last><first>Peter</first></author>
      <et-al/>
  </book>
</bib>
  

Adapted from XML Query Use Cases