Question: What was the population of Mashhad on September 11th, 1991?
Paraphrase: On September 11, 1991, how many people populated Mashhad?
SPARQL (Wikidata): SELECT ?obj WHERE { wd:Q121157 p:P1082 ?s . ?s ps:P1082 ?obj . ?s pq:P585 ?x filter(contains(YEAR(?x),'1991')) }