On k-strong and k-cyclic digraphs.

Jørgen Bang-Jensen Gregory Gutin Anders Yeo On k-strong and k-cyclic digraphs. 1-11 1996 162 Discrete Mathematics 1-3 http://dx.doi.org/10.1016/0012-365X(95)00300-L db/journals/dm/dm162.html#Bang-JensenGY96