A. Alhazov, R. Freund:
"On the Efficiency of P Systems with Active Membranes and Two Polarizations.";
Talk: Workshop on Membrane Computing, Milano, Italy; 2004-06-14 - 2004-06-16; in: " Pre-proceedings of the Fifth Workshop on Membrane Computing, Milano - Italy, June 2004 (WMC5)", G. Mauri, Gh. Paun, C. Zandron (ed.); (2004), 81 - 94.