1. Guilford, J. P. 1965.Fundamental Statistics in Psychology and Education, 4th ed., 248–250. New York: McGraw-Hill.
2. Models for testing the significance of combined results.
3. Netto, E. 1927.Lehrbuch der Combinatorik, 15New York: Chelsea.
4. Ray, W. S. 1960.An Introduction to Experimental Design, 231–233. New York: Macmillan.
5. Siegel, S. 1956.Nonparametric Statistics for the Behavioral Sciences, 271New York: McGraw-Hill.