A group of girls sit back to back.
A group of girls are standing next to each other.
One can not be standing and sit simultaneously.
exists e1 s1 x1 x2 x3.(Theme(e1,s1) & Theme(s1,x3) & a_back(s1) & r_back(e1) & Actor(e1,x1) & v_sit(e1) & of(x1,x2) & n_girl(x2) & n_group(x1))
exists e1 x1 x2.(all x3.(n_other(x3) -> to(e1,x3)) & r_next(e1) & Actor(e1,x1) & v_stand(e1) & of(x1,x2) & n_girl(x2) & n_group(x1))