A counterexample to Tait's Hamiltonian Graph Conjecture given by Tutte (1946). A simpler counterexample was later given by Kozyrev and Grinberg.
See also Hamiltonian Circuit, Tait's Hamiltonian Graph Conjecture
References
Honsberger, R. Mathematical Gems I. Washington, DC: Math. Assoc. Amer., pp. 82-89, 1973.
Saaty, T. L. and Kainen, P. C. The Four-Color Problem: Assaults and Conquest. New York: Dover, p. 112, 1986.
Tutte, W. T. ``On Hamiltonian Circuits.'' J. London Math. Soc. 21, 98-101, 1946.