People in the city.
People are in a small town.
People can not be in a city and a small town at the same time.
exists x1 x2.(n_city(x2) & a_topic(x1) & in(x1,x2) & n_people(x1))
exists p1 x1.(exists s1 x2.(in(x1,x2) & n_town(x2) & a_small(s1) & Theme(s1,x2)) & n_people(x1))