Laure Gonnord Nicolas Halbwachs Pascal Raymond From Discrete Duration Calculus to Symbolic Automata. 3-18 2006 153 Electr. Notes Theor. Comput. Sci. 4 http://dx.doi.org/10.1016/j.entcs.2006.02.022 db/journals/entcs/entcs153.html#GonnordHR06