What is the {single} for {present in work} of {hard rock}
What single is portion of difficult rocks current work?
What single is part of hard rocks current work?
SELECT DISTINCT ?a WHERE { ?a rdf:type ontology:single . resource:hard_rock property:present_in_work ?a }
select distinct ?obj where { ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q83270> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1441> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj . ?obj <http://www.wikidata.org/entity/P31> <http://wikidata.dbpedia.org/resource/Q134556> } 
 select distinct ?obj where { wd:Q83270 wdt:P1441 ?obj . ?obj wdt:P31 wd:Q134556 } 