Question: What nations have a calling code of less than 506 and are located geographically in Central America?
Answer(s):
answer: El Salvador
answer: Guatemala
answer: Belize
answer: Honduras

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.01tzh)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.01tzh ns:location.location.contains ?x .
?x ns:common.topic.notable_types ns:m.01mp .
?x ns:location.country.calling_code ?num .
FILTER (xsd:integer(?num) < 506) . 
}