Two men playing guitars are singing at a concert.
The two women are singing at the concert.
The men can't be women.
exists e2 e1 x1 x2 x3 x4.(at(e2,x4) & n_concert(x4) & Actor(e2,x1) & v_sing(e2) & Theme(e1,x3) & Actor(e1,x2) & v_play(e1) & n_guitar(x3) & (x1 = x2) & n_man(x1) & card_eq_2(x1))
exists e1 x1 x2.(n_concert(x2) & n_woman(x1) & card_eq_2(x1) & at(e1,x2) & Actor(e1,x1) & v_sing(e1))