Question: Who is the writer of the singles whose producer is Peter-John Vettese?
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:producer <http://dbpedia.org/resource/Peter-John_Vettese> . ?x onto:writer ?uri  . ?x rdf:type onto:Single}