Question: What are the source of the streams whose one of the source is Calera, Oklahoma?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/source> <http://dbpedia.org/resource/Calera,_Oklahoma> . ?x <http://dbpedia.org/ontology/source> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Stream>}