Counterexample for Corneil's efficient algorithm for Graph Isomorphism
Mathon has shown that the conjecture used by Corneil and Gotlieb is false. The first reference states this fact.

1- P. Foggia, C.Sansone, M. Vento, A Performance Comparison of Five Algorithms for Graph Isomorphism, Proc. 3rd IAPR-TC15 Workshop Graph-Based Representations in Pattern Recognition, 2001, pp. 188-199.

2- R. Mathon, Sample graphs for isomorphism testing, Congressus Numerantium, 21, pp.
499-517, 1978