Two men on horseback watch as another man is thrown from his bucking horse.
Two men are riding a horse.
One must be riding a horse to be on horseback.
exists e1 e2 x1 x2 x3 x4 x5.(from(e1,x5) & n_horse(x5) & Actor(e2,x5) & v_buck(e2) & of(x5,x2) & n_male(x2) & Theme(e1,x1) & v_throw(e1) & as(x1,x4) & n_man(x4) & -(x4 = x1) & n_man(x1) & n_man(x1) & on(x1,x2) & n_watch(x2) & of(x2,x3) & n_horseback(x3) & card_eq_2(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_horse(x2) & n_man(x1) & card_eq_2(x1))