Francesco Bernardini Marian Gheorghe Maurice Margenstern Sergey Verlan Producer/Consumer in Membrane Systems and Petri Nets. 43-52 2007 conf/cie/2007 CiE http://dx.doi.org/10.1007/978-3-540-73001-9_5 db/conf/cie/cie2007.html#BernardiniGMV07