Group of runners participate in a marathon.
Runners are racing at the Boston Marathon.
Not all marathons are the Boston Marathon.
exists e1 x1 x2 x3.(ne_org_group(x1) & in(e1,x3) & n_marathon(x3) & Actor(e1,x1) & v_participate(e1) & of(x1,x2) & n_runner(x2))
exists e1 x1 x2 x3.(ne_org_marathon(x2) & (x2 = x3) & ne_org_boston(x3) & at(e1,x2) & Actor(e1,x1) & v_race(e1) & n_runner(x1))