L. Caccetta and R. Häggkvist, On minimal digraphs with given girth, Proceedings of the Ninth Southeastern Conference on Combinatorics, Graph Theory, and Computing, pp.181-187, 1978.

Y. Guo and L. Volkmann, Cycles in Multipartite Tournaments, Journal of Combinatorial Theory, Series B, vol.62, issue.2, pp.363-366, 1994.
DOI : 10.1006/jctb.1994.1075

C. T. Hò-ang and B. Reed, A note on short cycles in digraphs, pp.103-107, 1987.

B. D. Sullivan, A summary of results and problems related to the Caccetta-Häggkvist conjecture, preprint

M. Tewes and L. Volkmann, Vertex deletion and cycles in multipartite tournaments, Discrete Math, pp.769-779, 1999.
DOI : 10.1016/s0012-365x(99)90145-0

URL : http://doi.org/10.1016/s0012-365x(99)90145-0

C. Thomassen, The 2-linkage problem for acyclic digraphs, Discrete Math, pp.73-87, 1985.