Motorcyclists racing on a track.
Motorcyclists racing on a track which is dirt.
not every track is dirt
exists e1 x1 x2 x3.(a_topic(x1) & on(e1,x3) & n_track(x3) & Actor(e1,x2) & v_race(e1) & (x1 = x2) & n_motorcyclist(x1))
exists e1 p1 x1 x2 x3 x4.(a_topic(x1) & on(e1,x3) & exists x5.((x4 = x5) & n_dirt(x5)) & (x3 = x4) & n_track(x3) & Actor(e1,x2) & v_race(e1) & (x1 = x2) & n_motorcyclist(x1))