Sergey Verlan Francesco Bernardini Marian Gheorghe Maurice Margenstern Generalized communicating P systems. 170-184 2008 404 Theor. Comput. Sci. 1-2 http://dx.doi.org/10.1016/j.tcs.2008.04.008 db/journals/tcs/tcs404.html#VerlanBGM08