Question: Which of the Harry Potter books were published before 21 June 2003?
Answer(s):
answer: Harry Potter and the Chamber of Secrets
answer: Harry Potter and the Prisoner of Azkaban
answer: Harry Potter and the Philosopher's Stone
answer: Harry Potter and the Goblet of Fire

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.03647x)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.03647x ns:book.book_character.appears_in_book ?x .
?x ns:book.written_work.date_of_first_publication ?num .
FILTER (?num < "2003-06-21"^^xsd:dateTime) . 
}