Question: Who wrote the singles on the Main Course?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/album> <http://dbpedia.org/resource/Main_Course> . ?x <http://dbpedia.org/property/writer> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Single>}