Question: How many subjects are covered in the publications of Doubleday?
SPARQL query: SELECT DISTINCT COUNT(?uri) WHERE { ?x <http://dbpedia.org/ontology/publisher> <http://dbpedia.org/resource/Doubleday_(publisher)> . ?x <http://dbpedia.org/ontology/nonFictionSubject> ?uri  . }
Answer: There are [143] non-fiction subjects of the books published by Doubleday.