1. Aitken, A. C. Determinants and matrices. Edinburgh: Oliver and Boyd, 1939.
2. Duncan, W. J., Frazer, R. A., and Collar, A. R. Elementary matrices. England: Univ. Cambridge Press, 1938. Chap. IV.
3. Guttman, Louis. Properties of Gramian matrices. Chapter Two inThe prediction of quantitative variates by factor analysis. Doctoral dissertation, Univ. Minnesota, 1942.
4. Holzinger, Karl J. and Harman, Harry H. Factor analysis. Chicago: Univ. Chicago Press, 1941.
5. Horst, Paul. A method of factor analysis by means of which all coordinates of the factor matrix are given simultaneously.Psychometrika, 1937,2, 225–236.