question: Was M0 employed by M1 , employed by M2 , and employed by M3
query: SELECT count(*) WHERE {
  M0 ns:people.person.employment_history/ns:business.employment_tenure.company M1 .
  M0 ns:people.person.employment_history/ns:business.employment_tenure.company M2 .
  M0 ns:people.person.employment_history/ns:business.employment_tenure.company M3
  }