1. Aczél, J., 1996. Lectures on Functional Equations and Their Applications. Mathematics in Science and Engineering, Vol. 19, Academic Press, New York
2. Adeli, H., Hung, S., 1996. Machine Learning. Neural Networks, Genetic Algorithms, and Fuzzy Systems. Wiley, New York
3. Atkinson, K.E., 1989. An Introduction to Numerical Analysis. Wiley, New York
4. Castillo, E., Ruiz-Cobo, R., 1992. Functional Equations in Science and Engineering. Marcel Dekker, New York
5. Castillo, E., 1998. Functional Networks. Neural Processing Letter, Vol. 7, pp. 151–159