A group of girls sit back to back.
A group of girls are sitting with their backs to each other.
Sentence one says a group of girls are sitting back to back Sentence two says the group of girls are sitting with their backs to each other, or back to back
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 x3.(all x4.(n_other(x4) -> to(e1,x4)) & with(e1,x3) & n_back(x3) & of(x3,x1) & n_thing(x1) & Actor(e1,x1) & v_sit(e1) & of(x1,x2) & n_girl(x2) & n_group(x1))