What is {operator} of {London Underground} that is {end time} is {1969-12-31} ?
On December 31st, 1969, what was the factor of that completed the London Underground.
What was the operator of the London Underground that finished in December 31st, 1969?
SELECT ?t WHERE { ?b property:end_time ?q . ?b property:operator ?t . FILTER ( CONTAINS ( YEAR ( ?q ) , '1969' ) ) . resource:London_Underground property:operator ?b }
select distinct ?obj  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q20075> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P137> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
?statement <http://www.wikidata.org/entity/P582> <1969-12-31>
} 

SELECT ?obj WHERE { wd:Q20075 p:P137 ?s . ?s ps:P137 ?obj . ?s pq:P582 ?x filter(contains(YEAR(?x),'1969')) }