B. Schölkopf, K. K. Sung, C. J. C. Burges, F. Girosi, P. Niyogi, T. Poggio, V. Vapnik,
                           "Comparing support vector machines with gaussian kernels to radial basis function
                           classifiers", IEEE Transactions on Signal Processing, Vol. 45, No. 11, pp. 2758-2765,
                           1997
