Dominique Perrin and Marcel-Paul Schützenberger. Synchronizing prefix codes and automata and the road coloring problem. In Symbolic dynamics and its applications (New Haven, CT, 1991), volume 135 of Contemp. Math., pages 295–318. Amer. Math. Soc., Providence, RI, 1992.

Alain Lascoux and Marcel-Paul Schützenberger. Décompositions dans l'algèbre des différences divisées. Discrete Math., 99(1-3):165–179, 1992.

Christophe Reutenauer and Marcel-Paul Schützenberger. Rational word functions: characterization and minimization. In Words, Languages and Combinatorics (Kyoto, 1990), pages 435–443. World Sci. Publishing, River Edge, NJ, 1992.