Three men on a dirty river.
Guys are on a body of water.
The guys are on a body of water that is a dirty river.
exists x1 x2 x3.(a_topic(x1) & on(x1,x2) & n_river(x2) & of(x2,x3) & n_dirty(x3) & n_man(x1) & card_eq_3(x1))
exists p1 x1.(exists x2 x3.(on(x1,x2) & of(x2,x3) & n_water(x3) & n_body(x2)) & n_guy(x1))