question: Was a American person influenced by M1 and M2 and influenced by M3
query: SELECT count(*) WHERE {
  ?x0 a ns:people.person .
  ?x0 ns:influence.influence_node.influenced_by M1 .
  ?x0 ns:influence.influence_node.influenced_by M2 .
  ?x0 ns:influence.influence_node.influenced_by M3 .
  ?x0 ns:people.person.nationality ns:m.09c7w0
  }