Question: Which class of political system, does where the currency Korean yen is used have?
Answer(s):
answer: Juche
answer: Socialist state
answer: Single-party state

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:location.country.currency_formerly_used ns:m.09z6yw . 
?c ns:location.country.form_of_government ?x .
}