1. Brigham, C. C. 1932.A study of error, xiv+384New York: Coll. Entrance Exam. Board.
2. Brown, W. and Thomson, G. H. 1925.The essentials of mental measurement., 3rd ed., 234London: Cambridge Univ. Press.
3. Dunlap, J. W. and Kurtz, A. K. 1932.Handbook of statistical nomographs, tables, and formulas, x+163New York: World Book Co.
4. Holzinger, K. J. 1928.Statistical methods for students in education, viii+372Boston: Ginn.
5. Kelley, T. L. 1924.Statistical method, xi+390New York: Macmillan.