Question: What cities does the river goes through, whose tributary is the little black river in Arkansas?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/leftTributary> <http://dbpedia.org/resource/Little_Black_River_(Missouri_-_Arkansas)> . ?x <http://dbpedia.org/ontology/city> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/River>}