1. On minimal regular digraphs with given girth
2. Minimal 2-regular digraphs with given girth
3. Graphs and hypergraphs. North Holland, Amsterdam (1973).
4. 1-graphes réguliers minimaux de girth donné. Cahiers du C.E.R.O., Bruxelles (1975) 123–135.
5. and , On minimal digraphs with given girth. Congressus Numerantium XXI. Edited by , , and . Utilitas Mathematica, Boca Raton (1978) 181–187.