[1] M. Behzad G. Chartrand:
No graph is perfect. Amer. Math. Monthly 74 (1967), 962-963.
MR 0220627
[2] M. Behzad G. Chartrand:
Introduction to the Theory of Graphs. Allyn and Bacon, Inc., Boston 1971.
MR 0432461
[3] /. Sedláček:
O perfektních a kvaziperfektních grafech. Čas. pěst. mat. 100 (1975), 135 - 141.
MR 0416994