Four people are singing Karaoke.
They are singing a Billy Joel song.
People singing Karaoke do not always sing Billy Joel songs.
exists e1 x1 x2.(ne_nam_karaoke(x2) & Theme(e1,x2) & Actor(e1,x1) & v_sing(e1) & n_people(x1) & card_eq_4(x1))
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_sing(e1) & n_song(x2) & (x2 = x3) & ne_org_joel(x3) & (x2 = x1) & ne_org_billy(x1) & n_thing(x1))