1. [Arn85] Arnold, A.: A syntactic congruence for rational ?-languages. Theoret. Comput. Sci.39, 333?335 (1985)
2. Lect. Notes Math.;P. Cartier,1969
3. [CMZ89] Cori, R., Métivier, Y., Zielonka, W.: Asynchronous mappings and asynchronous cellular automata. Tech. rep. 89-97, LABRI, Univ. Bordeaux, 1989
4. [CP85] Cori, R., Perrin, D.: Automates et commutations partielles. R.A.I.R.O.?Inf. Théor. Appl.19, 21?32 (1985)
5. Lect. Notes Comput. Sci.;V. Diekert,1990