“…This last resuit and another equivalent proposition concerning the structure of the 0-minimal idéal of the syntactic semigroups S (A), give a characterization of free subsemigroups, of a free semigroup, having a bounded synchronization delay which is more gênerai than that of the theorem of Restivo [11], and also that of a recent resuit obtained by the author, D. Perrin, A. Restivo and S. Termini [3] under the hypothesis that A is finitely gênerated.…”