What film producer was employed by M1 , employed by M2 and M3 , and employed by a film distributor
SELECT DISTINCT ?x0 WHERE {
?x0 a ns:film.producer .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company ?x1 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M1 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M2 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M3 .
?x1 a ns:film.film_distributor
}