An Upper Bound for the Number of Hamiltonian Cycles on a Symmetric Diagraph

Jinshan Zhang An Upper Bound for the Number of Hamiltonian Cycles on a Symmetric Diagraph http://arxiv.org/abs/0712.0616 2007 CoRR abs/0712.0616 db/journals/corr/corr0712.html#abs-0712-0616 informal publication