Key points are not available for this paper at this time.
A graph G with vertex set N = 1, 2,. -. , n is called a permutation graph there exists a permutation P on N such that for i, j E N, (i -j) P-' (i) -P-' (j) < 0 if ar only if i and j are joined by an edge in G.
Even et al. (Sat,) studied this question.