Two men singing at an event.
Two women singing at an event.
Either two women or two men are singing.
exists e1 x1 x2 x3.(a_topic(x1) & at(e1,x3) & n_event(x3) & Actor(e1,x2) & v_sing(e1) & (x1 = x2) & n_man(x1) & card_eq_2(x1))
exists e1 x1 x2 x3.(a_topic(x1) & at(e1,x3) & n_event(x3) & Actor(e1,x2) & v_sing(e1) & (x1 = x2) & n_woman(x1) & card_eq_2(x1))