Question: Which fields are covered by academic journals in the US?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/country> <http://dbpedia.org/resource/United_States> . ?x <http://dbpedia.org/property/discipline> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/AcademicJournal>}