1. M. Behzad, G. Chartrand andC. Wall, On minimal regular digraphs with given girth,Fund. Math. 69 (1970), 227–231.
2. M. Behzad, Miminally 2-regular digraphs with given girth,J. Math. Soc. of Japan 25 (1973), 1–6.
3. C. Berge,Graphes et hypergraphes, Dunod, Paris (1970).
4. J. C. Bermond, 1-graphes réguliers de girth donné,Cahiers du C.E.R.O. Bruxelles 17 (1975), 123–135.
5. L. Caccetta andR. Häggkvist, On minimal digraphs with given girth,Congressus numerantium XXI, Utilitas Mathematica, Boca Raton (1978), 181–187.