1. Cooley, W.W. and Lohnes, P.R. 1971.Multivariate Data Analysis, 364–364. New York: John Wiley.
2. Morrison, D.F. 1967.Multivariate Statistical Methods, 338–338. New York: McGraw-Hill.
3. Overall, J.E. and Klett, C.J. 1972.Applied Multivariate Analysis, 500–500. New York: McGraw-Hill.