1) FISHER R. A. The use of multiple measurements in taxonomic problems. Annals of Eugenics London. (1936) vol.7, p.179-188.
2) BEZDEK J. C. Pattern Recognition with Fuzzy Objective Function Algorithms. Plenum Press, New York. (1981)
3) HOSMER D. W. Jr. Maximum likelihood estimates of the parameters of a mixture of two regression lines. Communications in Statistics. (1974) vol.3, no.10, p.995-1005.