1. Lloyd, S.P.: Least square quantization in PCM. IEEE Trans. Inform. Theory 28, 129–137 (1982)
2. Ball, G.H., Hall, D.J.: PROMENADE-an on-line pattern recognition system. Stanford Research Inst. Menlo Park, Stanford University (1967)
3. Tou, J., Gonzalez, R.: Pattern Recognition Principles, p. 377. Addision-Wesley, Reading (1977)
4. Astrahan, M.M.: Speech analysis by clustering (1970)
5. Kaufman, L., Rousseeuw, P.J.: Finding Groups in Data: An Introduction to Cluster Analysis, p. 342. Wiley, New York (1990)