In: Inform. Theor. Appl., Vol. 21, No. 4, pages 469-477. 1987. In French.
Abstract: It is shown that every labelled graph with a distinguishable mode can be constructively transformed into a graph with the same set of labels and a particular shape that the author calls a cactus. The result is applicable in various areas of informatics, such as in the structuring of the program schemas and in Petri nets for the transformation of the covering graph into one which is easier to manipulate.