Several birds flying in front of trees.
Birds are flying in the sky.
Birds means more than one which can be several. and in front of trees is in the sky
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & in(e1,x3) & of(x3,x4) & n_tree(x4) & n_front(x3) & Actor(e1,x2) & v_fly(e1) & (x1 = x2) & n_bird(x1) & a_several(s1) & Theme(s1,x1))
exists e1 x1 x2.(n_sky(x2) & in(e1,x2) & Actor(e1,x1) & v_fly(e1) & n_bird(x1))