A cowboy riding a bucking horse with the letters CKI marked on its backside.
The cowboy was riding a mechanical bull.
A bucking horse and a mechanical bull are two different things.
exists e1 e2 x1 x2 x3 x4 x5 x6 x7 x8.(n_backside(x8) & of(x8,x5) & n_thing(x5) & ne_org_cki(x6) & n_letter(x5) & a_topic(x1) & with(e1,x5) & on(e2,x8) & Theme(e2,x7) & Actor(e2,x6) & v_mark(e2) & (x5 = x7) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_horse(x3) & of(x3,x4) & n_bucking(x4) & (x1 = x2) & n_cowboy(x1))
exists e1 s1 x1 x2.(n_cowboy(x1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bull(x2) & a_mechanical(s1) & Theme(s1,x2))