Long Cycles in Digraphs
Carsten Thomassen · Proceedings of the London Mathematical Society · 1981
By Ghouila-Houri's theorem [10], every strong digraph of order n and with minimum degree at least n is Hamiltonian. Extensions of this theorem can be found in [11, 13, 16, 18]. Nash-Williams [15] raised the problem of describing all the extreme digraphs for Ghouila-Houri's