A few horses race each other on the track.
A few horses race each other for a chance to win the derby.
Horses racing on a track does not mean they are in a derby.
exists x4.(n_track(x4) & all x1.(n_other(x1) -> exists s1 x2 x3.(a_topic(x2) & on(x2,x4) & for(x2,x1) & n_race(x2) & of(x2,x3) & n_horse(x3) & a_few(s1) & Theme(s1,x2))))
exists x5.(n_derby(x5) & all x1.(n_other(x1) -> exists p1 s1 x2 x3 x4.(a_topic(x2) & for(x2,x4) & Topic(x4,p1) & exists e1.(Theme(e1,x5) & Actor(e1,x4) & v_win(e1)) & n_chance(x4) & for(x2,x1) & n_race(x2) & of(x2,x3) & n_horse(x3) & a_few(s1) & Theme(s1,x2))))