Adams, J. F. "An Evaluation of the Effect of Level of Item Difficulty on Various Indices of Item-Discrimination." Unpublished Ph.D. thesis, Washington State University, 1959.
2.
Aschenbrenner, R. "A Table of Values of the Product Moment Coefficient of Correlation as Determined by the Proportions of Successes on the X-Variable in Each Ten Percent Tail of the Y-Variable Distribution." Iowa City: University Examinations Serivce of the State University of Iowa, 1949.
3.
Davidoff, M. D. and Goheen, H. W. "A Table for the Rapid Determination of the Tetrachoric Correlation Coefficient." Psychometrika, XVIII (1953),115-121.
4.
Flanagan, J. C. "A Table of the Values of the Product-Moment Coefficient of Correlation in a Normal Bivariate Population Corresponding to Given Proportions of Successes." Pittsburgh : American Institute for Research, 1950.
5.
Flanagan, J. C. "The Effectiveness of Short Methods for Calculating Correlation Coefficients." Psychological Bulletin, XLIX (1952), 342-348.
6.
Humphreys, L. G. "Commonly Used Statistical Procedures." In J. P. Guilford (Ed.), Printed Classification Tests: Aviation Psychology Research Report #5. Washington, D. C.: Government Printing Office, 1947.
7.
Jurgensen, C. E. "Table for Determining Phi Coefficients." Psychometrika, XII (1947), 17-29.
