Question: Which WWII era US president was once White House Chief of Staff?
Answer(s):
answer: Harry S. Truman

SPARQL query:
#MANUAL SPARQL
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
  ns:m.081pw ns:time.event.start_date ?start ;
             ns:time.event.end_date ?end .
  ?x ns:government.politician.government_positions_held  ?y .
  ?y ns:government.government_position_held.office_position_or_title ns:m.060d2 ; # President of the United States
     ns:government.government_position_held.from  ?from ;
     ns:government.government_position_held.to  ?to .
  FILTER (?from < ?end)
  FILTER (?to > ?start)?x ns:government.political_appointer.appointees ?c .
?c ns:government.government_position_held.office_position_or_title ns:m.01f62w . 
}