A girl on a bike stops to look back.
A girl is wearing a bike helmet.
Not all bike riders are wearing a helmet.
exists e1 p1 x1 x2.(Topic(e1,p1) & Actor(e1,x1) & v_stop(e1) & exists e2 p2.(exists s1.(Theme(s1,x1) & a_back(s1)) & Topic(e2,p2) & Actor(e2,x1) & v_look(e2)) & on(x1,x2) & n_bike(x2) & n_girl(x1))
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_wear(e1) & n_helmet(x2) & of(x2,x3) & n_bike(x3) & n_girl(x1))