What is {head of government} of {Düsseldorf} that is {start time} is {1820-7-19} ?
Who was the head of government of Dusseldorf in 1820?
Who is {head of government} of {Düsseldorf} whose {start time} is {1820-7-19} ?
SELECT ?p WHERE { ?k property:start_time ?p . resource:Düsseldorf property:head_of_government ?k . ?k property:head_of_government ?p . FILTER ( CONTAINS ( YEAR ( ?p ) , '1820' ) ) }
select distinct ?obj  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q1718> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P6> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
?statement <http://www.wikidata.org/entity/P580> <1820-7-19>
} 

SELECT ?obj WHERE { wd:Q1718 p:P6 ?s . ?s ps:P6 ?obj . ?s pq:P580 ?x filter(contains(YEAR(?x),'1820')) }