machine_question: what were adolf hitler 's parents names and the person's date of death is before 1907-12-21
question: What were the names of Adolf Hitler's parents and which one died before Dec 21, 1907?
sparql: PREFIX ns: <http://rdf.freebase.com/ns/>
  SELECT DISTINCT ?x
  WHERE {
  FILTER (?x != ns:m.07_m9_)
  FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
  ns:m.07_m9_ ns:people.person.parents ?x .
  ?x ns:people.deceased_person.date_of_death ?num .
  FILTER (?num < "1907-12-21"^^xsd:dateTime) . 
  }
webqsp_question: what were adolf hitler 's parents names