Who trained the wrestlers who are billed in Wisconsin?
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/billed> <http://dbpedia.org/resource/Wisconsin> . ?x <http://dbpedia.org/ontology/trainer> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Wrestler>}
Wisconsin