A skull of rowers on a lake.
People are on the lake.
People can be rowers.
exists x1 x2 x3.(a_topic(x1) & of(x1,x2) & on(x2,x3) & n_lake(x3) & n_rower(x2) & n_skull(x1))
exists p1 x1 x2.(n_lake(x2) & on(x1,x2) & n_people(x1))