1. Cluster analysis for applications;Anderberg,1973
2. Backer, E., Cluster analysis formalized as a process of fuzzy identification based on fuzzy relations, Delft University of Technology, Department of Electrical Engineering, Report IT-78-15, October 1978.
3. A clustering technique for summarizing variate data;Ball;Behavorial Science,1967
4. Charles, C., Lechevallier, Y., Pattern recognition by a piecewise polynomial approximation with variable points, IRIA Laboria, Report No. 338, 1979.
5. Chernoff, M., Metric consideration in cluster analysis, Proc. 6th Berkley Symposium on Math. Statistics and Probability, 1970.