Two girls sit back to back.
two girls are sitting together.
Sitting back to back is similar to sitting together.
exists e1 s1 x1 x2.(Theme(e1,s1) & Theme(s1,x2) & a_back(s1) & r_back(e1) & Actor(e1,x1) & v_sit(e1) & n_girl(x1) & card_eq_2(x1))
exists e1 p1 x1.(exists s1.(Theme(s1,x1) & a_together(s1)) & Topic(e1,p1) & Actor(e1,x1) & v_sit(e1) & n_girl(x1) & card_eq_2(x1))