Question: What are the non-fiction topics in the books whose authors is Terry Pratchett?
SPARQL query:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX prop: <http://dbpedia.org/property/>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT DISTINCT ?uri WHERE { ?x prop:author <http://dbpedia.org/resource/Terry_Pratchett> . ?x onto:nonFictionSubject ?uri  . ?x rdf:type onto:Book}