Question: Which river's mouth location is Laptev Sea and also Arctic Ocean?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?uri <http://dbpedia.org/property/mouthLocation> <http://dbpedia.org/resource/Laptev_Sea> . ?uri <http://dbpedia.org/property/mouthLocation> <http://dbpedia.org/resource/Arctic_Ocean> . }