Question: Which money system is used by the location where the wine regions that produce Retsina wine style?
Answer(s):
answer: Euro

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ?c)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
?c ns:wine.wine_region.wine_styles ns:m.01jg9j . 
?c ns:location.country.currency_used ?x .
}