Haiming Chen Mihai Ionescu Tseren-Onolt Ishdorj Andrei Paun Gheorghe Paun Mario J. Pérez-Jiménez Spiking neural P systems with extended rules: universality and languages. 147-166 2008 7 Natural Computing 2 http://dx.doi.org/10.1007/s11047-006-9024-6 db/journals/nc/nc7.html#ChenIIPPP08