PREFIX : <http://example/>
PREFIX  dc:     <http://purl.org/dc/elements/1.1/>

SELECT ?a
FROM <D.ttl>
{
  ?b dc:title ?title .
  SERVICE <http://sparql.org/books>
     { ?s dc:title ?title . ?s dc:creator ?a }
}


## GROUP BY ?s ?p
## HAVING COUNT(?o) > 2