E. Best, R. Devillers, and J. Esparza. General refinement and recursion operators for the Petri box calculus. In Patrice Enjalbert et al., editor, 10th Annual Symposium on Theoretical Aspects of Computer Science 1993 (10th STACS '93), number 665 in Lecture Notes in Computer Science, pages 130–140, 1993.	Info
J. Desel and J. Esparza. Reachability in cyclic extended free-choice systems. Theoretical Computer Science, 114:93–118, 1993.	PDF (2 MB) Info Conference version
J. Esparza and B. von Stengel:. The asynchronous committee meeting problem. In Jan van Leuween, editor, Proceedings of WG '93, Graph-Theoretic in Computer Science, 19th International Workshop, number 790 in Lecture Notes in Computer Science, pages 276–287, 1993.	GZipped PostScript (43 kB) PDF (179 kB) Info