Question: Which of the three countries which border Mexico has a country calling code of 501?
Answer(s):
answer: Belize

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.0b90_r)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.0b90_r ns:location.location.adjoin_s ?y .
?y ns:location.adjoining_relationship.adjoins ?x .
?x ns:common.topic.notable_types ns:m.01mp .
?x ns:location.country.calling_code "501" . 
}