E. L. B. Junior, C. R. B. Azevedo, W. T. A. Lopes, M. S. Alencar, and F. Madeiro, “Methods to Accelerate a Competitive Learning Algorithm Applied to VQ Codebook Desing”, Trends Comput. Appl. Math., vol. 11, no. 3, pp. 193–203, Jun. 2010.