Question: Which non fiction of the Thud is also the field of the Jon Speelman ?
SPARQL:
 SELECT DISTINCT ?uri WHERE { <http://dbpedia.org/resource/Thud!> <http://dbpedia.org/ontology/nonFictionSubject> ?uri. <http://dbpedia.org/resource/Jon_Speelman> <http://dbpedia.org/ontology/field> ?uri}