What is the {unit of density} for {measured by} of {density}
who unit of thickness for measured by of density?
who unit of density for measured by of density?
SELECT DISTINCT ?b WHERE { resource:density property:measurement_scale ?b . ?b rdf:type ontology:unit_of_density }
select distinct ?obj where { ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q29539> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1880> . ?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/Q10387685> } 
 select distinct ?obj where { wd:Q29539 wdt:P1880 ?obj . ?obj wdt:P31 wd:Q10387685 } 