1. Thurstone, L. L. Multiple-factor analysis. Chicago: Univ. Chicago Press, 1947.
2. Thomson, G. H. The factorial analysis of human ability. London: Univ. London Press, 1948.
3. Pearson, K. On the influence of natural selection on the variability and correlation of organs.Phil. Trans. roy. Soc. 1902 A,200, 1–66.
4. Aitken, A. C. Note on selection from a multivariate normal population.Proc. Edin. math. Soc., 1934,4, 106–110.
5. Thomson, G. H. The influence of univariate selection on the factorial analysis of ability.Brit. J. Psychol., 1938,28, 451–459.