T. Yoshizawa. Recent developments in clustering and data analysis: Proceedings of the Japanese-French Scientific Seminar, March 24-26, 1987., Academic Press, Boston, (1988)
T. Wansbeek, and J. Buyze. Research Report BPA, 13593-81-M1. Department for Statistical Methods, Central Bureau of Statistics, Voorburg, The Netherlands, (1981)
C. Veldscholte, G. Antonides, and P. Kroonenberg. Research Report, R9519/A. Rotterdam Institute for Business Economic Studies, Erasmus University, Rotterdam, The Netherlands, (1995)