Question: What structure opened in 01/09/1975 and is where the Celtics practice?
Answer(s):
answer: XL Center

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.0bwjj)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.0bwjj ns:sports.sports_team.arena_stadium ?x .
?x ns:architecture.structure.opened "1975-01-09"^^xsd:dateTime . 
}