walter vromans was an assistant at which football match that has a start date that is less than or equal to 2010-06-29t16:00:00-08:00?
Entity Entity Entity
m.0c44msd m.0c22yr_ m.0c1lvg1
2010 FIFA World Cup Group C - USA ./. ALG 2010 FIFA World Cup Round of 16 - PAR ./. JPN 2010 FIFA World Cup Group B - ARG ./. KOR
class entity literal
soccer.football_match m.0c0mfbj 2010-06-29T16:00:00-08:00^^http://www.w3.org/2001/XMLSchema#dateTime
soccer.football_match soccer.football_referee type.datetime
Football Match Walter Vromans 2010-06-29T16:00:00-08:00
none none <=
soccer.football_referee.assistant_referee_at time.event.start_date
Assistant referee at Start date
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> PREFIX : <http://rdf.freebase.com/ns/> 
SELECT (?x0 AS ?value) WHERE {
SELECT DISTINCT ?x0  WHERE { 
?x0 :type.object.type :soccer.football_match . 
VALUES ?x1 { :m.0c0mfbj } 
FILTER (?x2 <= "2010-06-29T16:00:00-08:00"^^<http://www.w3.org/2001/XMLSchema#dateTime>)
?x1 :soccer.football_referee.assistant_referee_at ?x0 . 
?x0 :time.event.start_date ?x2 . 
FILTER ( ?x0 != ?x1 && ?x0 != ?x2 && ?x1 != ?x2  )
}
}
(AND soccer.football_match (AND (JOIN (R soccer.football_referee.assistant_referee_at) m.0c0mfbj) (le time.event.start_date 2010-06-29T16:00:00-08:00^^http://www.w3.org/2001/XMLSchema#dateTime)))