Martínez-del-Amor, M. A., Pérez-Hurtado I., Pérez-Jiménez M. J., Riscos-Núñez A., & Sancho-Caparrini F.  (2011).??A simulation algorithm for multienvironment probabilistic P systems: A formal verification.  International Journal of Foundations of Computer Science. 22(1),?107-118.