1. Etiquetage des structures d'événements du point de vue des ordres et des graphes;Assous;Rapport de Recherche du Laboratoire de l'Informatique du Parallélisme,1989
2. Solution to advanced problem No. 4526;Descartes;Amer. Math. Monthly,1954
3. A decomposition theorem for partially ordered sets;Dilworth;Ann. of Math.,1950
4. On a problem of formal logic;Ramsey;Proc. London Math. Soc.,1930
5. B. Rozoy, Distributed languages, a context dependent extension of traces, in Proc. 3rd Workshop on Concurrency, Goslar, Germany, March 1991; Theoret. Comput. Sci., to appear.