Three passengers on a train car.
They are in a train.
They can refer Three passengers.
exists x1 x2 x3.(a_topic(x1) & on(x1,x2) & n_car(x2) & of(x2,x3) & n_train(x3) & n_passenger(x1) & card_eq_3(x1))
exists p1 x1.(n_thing(x1) & exists x2.(in(x1,x2) & n_train(x2)))