PREFIX xsd:  <http://www.w3.org/2001/XMLSchema#> 
PREFIX rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dc:   <http://purl.org/dc/elements/1.1/>

ASK {
  ?erdoes rdf:type foaf:Person .
  ?erdoes foaf:name "Paul Erdoes"^^xsd:string .
  {
    ?document dc:creator ?erdoes .
    ?document dc:creator ?author .
    ?document2 dc:creator ?author .
    ?document2 dc:creator ?author2 .
    ?author2 foaf:name ?name
    FILTER (?author!=?erdoes &&
            ?document2!=?document &&
            ?author2!=?erdoes &&
            ?author2!=?author)
  } UNION {
    ?document dc:creator ?erdoes .
    ?document dc:creator ?author .
    ?author foaf:name ?name 
    FILTER (?author!=?erdoes)
  }
}