Which cities have the river one of whose Tributary is the Missouri's big spring?
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/rightTributary> <http://dbpedia.org/resource/Big_Spring_(Missouri)> . ?x <http://dbpedia.org/ontology/city> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/River>}
Big_Spring_(Missouri)