What is {chairperson} of {University of Waterloo} that is {end time} is {1981-6-0} ?
When the University of Waterloo's post came to an end, who was the chairperson?
Who was the Chairperson of University of waterloo while that post was came to an end in 1981
SELECT ?i WHERE { FILTER ( CONTAINS ( YEAR ( ?f ) , '1981' ) ) . ?l property:end_time ?f . resource:University_of_Waterloo property:chairperson ?l . ?l property:chairperson ?i }
select distinct ?obj  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q1049470> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P488> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
?statement <http://www.wikidata.org/entity/P582> <1981-6-0>
} 

SELECT ?obj WHERE { wd:Q1049470 p:P488 ?s . ?s ps:P488 ?obj . ?s pq:P582 ?x filter(contains(YEAR(?x),'1981')) }