1. "[1] B. ALBERTS, A. JOHNSON, J. LEWIS, M. RAFF, K. ROBERTS, P. WALTER, Molecular Biology of the Cell, 4th ed. Garland Science, New York, 2002.
2. [2] C. CHOFFRUT, J. KARHUMA¨ KI, Combinatorics on words, In [12], vol. I, pp. 329-438.
3. [3] W. GERSTNER, W. KISTLER, Spiking Neuron Models. Single Neurons, Populations, Plasticity,Cambridge Univ. Press, 2002.
4. [4] M. IONESCU, Gh. PA˘ UN, T. YOKOMORI, Spiking neural P systems, Fundamenta Informaticae, 71(2-3), pp. 279-308.
5. [5] M. LOTHAIRE, Combinatorics on Words, Addison-Wesley, Reading, Mass., 1983.