People are holding signs and marching.
A group is celebrating an important event.
People can hold signs and march without celebrating an important event.
exists e1 x1 x2 x3 x4.(Theme(e1,x2) & Actor(e1,x1) & v_hold(e1) & n_march(x4) & n_sign(x3) & subset_of(x4,x2) & subset_of(x3,x2) & n_people(x1))
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_celebrate(e1) & n_event(x2) & a_important(s1) & Theme(s1,x2) & n_group(x1))