<bib>
{
  for $b in distinct-values(doc("XMP/bib.xml")/bib/book/author/last)
  return

  <author lname="{$b}">

    <book>
    {
      for $z in doc("XMP/bib.xml")/bib/book
      where $z/author/last=$b
      return
      <book>
        {$z/@year}
        {string($z/title)}
      </book>
    }
  </book>
  </author>
}
</bib>