Question: Who was the Canadian prime minister in 1993 that said "no, a proof is a proof"?
Answer(s):
answer: Jean Chrétien

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.060m4)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.060m4 ns:government.government_office_or_title.office_holders ?y .
?y ns:government.government_position_held.office_holder ?x .
FILTER(NOT EXISTS {?y ns:government.government_position_held.from ?sk0} || 
EXISTS {?y ns:government.government_position_held.from ?sk1 . 
FILTER(xsd:datetime(?sk1) <= "1993-12-31"^^xsd:dateTime) })
FILTER(NOT EXISTS {?y ns:government.government_position_held.to ?sk2} || 
EXISTS {?y ns:government.government_position_held.to ?sk3 . 
FILTER(xsd:datetime(?sk3) >= "1993-01-01"^^xsd:dateTime) })
?x ns:people.person.quotations ns:m.02sf4nd . 
}