Guilford, J. P.Fundamental statistics in psychology and education. Fourth edition. New York: McGraw-Hill, 1965.
2.
Gulliksen, H.Theory of mental tests. New York: Wiley, 1950 .
3.
Kelley, T. L.Statistical method. New York: Macmillan, 1923.
4.
Pearson, K.Mathematical contributions to the theory of evolution, XI. On the influence of natural selection on the variability and correlations of organs. Philosophical Transactions of the Royal Society (A), 1903, 200, 1-66.
5.
Pearson, K.On the influence of double selection on the variation and correlation of normal characters. Biometrika , 1908, 6, 111.
6.
Rydberg, S.Bias in prediction: On correction methods. Stockholm Studies in Educational Psychology 7. Uppsala: Almqvist & Wiksell, 1963.