R. Freund, M. Kogler:
"Computationally Complete Spiking Neural P Systems without Delay: Two Types of Neurons Are Enough";
in: "11th International Conference, CMC2010 - Membrane Computing", M. Gheorghe, Gh. Paun et al. (ed.); issued by: LNCS; Springer LNCS, Heidelberg, 2010, ISBN: 3-642-18122-8, 198 - 208.