Question: Name the parents of the person who rote "Joe Williams Blues"?
Answer(s):
answer: Temperance Fitzgerald
answer: William Fitzgerald

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:music.lyricist.lyrics_written ns:m.01082g_w . 
?c ns:people.person.parents ?x .
}