Which person was employed by M1 and M2 , employed by M3 and M4 , and employed by M5 and M6
SELECT DISTINCT ?x0 WHERE {
?x0 a ns:people.person .
?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 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M4 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M5 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M6
}