A group of girls sit back to back.
The girls are sitting together.
The group of girls sitting together are 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 p1 x1.(n_girl(x1) & exists s1.(Theme(s1,x1) & a_together(s1)) & Topic(e1,p1) & Actor(e1,x1) & v_sit(e1))