Question: Which river starts from the county seat of Heathsville, Virginia?
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 onto:countySeat <http://dbpedia.org/resource/Heathsville,_Virginia> . ?uri prop:mouthLocation ?x . ?uri rdf:type onto:River}