Question: Which drug, invented by Albert Hofmann, is Charlie Sheen a frequent user of?
Answer(s):
answer: Lysergic acid diethylamide

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.01pllx)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.01pllx ns:base.popstra.celebrity.substance_abuse ?y .
?y ns:base.popstra.substance_abuse.substance ?x .
?x ns:law.invention.inventor ns:m.012mxb . 
}