What is <produced by> of <petroleum> ?
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Which is produced by petroleum?
SELECT DISTINCT ?a WHERE { ?a property:produced_by resource:petroleum }
select distinct ?answer where { ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject>  ?answer. ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P2849> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q22656>. }
select distinct ?answer where { ?answer wdt:P2849 wd:Q22656}
bitumen