Gutiérrez-Naranjo, M. A., Pérez-Jiménez M. J., & Romero-Campero F. J.  (2005).??Simulating Avascular Tumors with Membrane Systems.  (Miguel A. Gutiérrez-Naranjo, Agustín Riscos-Núñez, Francisco J. Romero-Campero, Dragos Sburlan, Ed.).Third Brainstorming Week on Membrane Computing.  185-195.