Question: Which river's mouth is located in Gulf of Mexico and has source location as Itasca State Park ?
SPARQL:
SELECT DISTINCT ?uri WHERE {?uri <http://dbpedia.org/ontology/riverMouth> <http://dbpedia.org/resource/Gulf_of_Mexico> . ?uri <http://dbpedia.org/property/sourceLocation> <http://dbpedia.org/resource/Itasca_State_Park>  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/River>}