Luca Bortolussi Alberto Policriti The Importance of Being (A Little Bit) Discrete. 75-92 2009 229 Electr. Notes Theor. Comput. Sci. 1 http://dx.doi.org/10.1016/j.entcs.2009.02.006 db/journals/entcs/entcs229.html#BortolussiP09