let $auction := doc("http://monetdb.cwi.nl/xmark/auctions.xml") return
let $ca := $auction/site/closed_auctions/closed_auction return
let
    $ei := $auction/site/regions/europe/item
for $p in $auction/site/people/person
let $a :=
  for $t in $ca
  where $p/@id = $t/buyer/@person
  return
    let $n := for $t2 in $ei where $t/itemref/@item = $t2/@id return $t2
    return <item>{$n/name/text()}</item>
return <person name="{$p/name/text()}">{$a}</person>