Question: How many people have managed a club which owns the Riverside Stadium?
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 COUNT(?uri) WHERE { ?x prop:ground <http://dbpedia.org/resource/Riverside_Stadium> . ?uri onto:managerClub ?x  . ?uri rdf:type onto:Person}