Question: What nation involved in the Vietnam War has a country calling code of 64?
Answer(s):
answer: New Zealand

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.07_nf)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.07_nf ns:military.military_conflict.combatants ?y .
?y ns:military.military_combatant_group.combatants ?x .
?x ns:location.country.calling_code "64" . 
}