[1] G. Chartrand F. Saba H. Zou: Edge rotations and distance between graphs. Časopispěst. mat. 100 (1975), 371-373.
[2] M. R. Garey D. S. Johnson:
Computers and Intractability: a guide to the theory of NP-copleteness. Freeman, San Francisco, 1979.
MR 0519066