Roberto Barbuti Andrea Maggiolo-Schettini Paolo Milazzo Simone Tini P Systems with Transport and Diffusion Membrane Channels. 17-31 2009 93 Fundam. Inform. 1-3 http://dx.doi.org/10.3233/FI-2009-0085 db/journals/fuin/fuin93.html#BarbutiMMT09