1. The 1938 Iowa Every-Pupil Basic Skills Testing Program,Bulletin of the State University of Iowa, New Series No. 937, October 23, 1938.
2. The tenth annual Iowa Every-Pupil High School Testing Program,Bulletin of the State University of Iowa, 1938.
3. Pearson, Karl. On the distribution of standard deviations of small samples.Biometrika, 1914–1915,10, 522–529.
4. Neyman, J. and Pearson, E. S. The problem ofK samples.Bulletin of the Polish Academy of Science, 1931.
5. Snedecor, G. W. Statistical Methods, Ames, Iowa. Collegiate Press, Inc., 1938. See also Fisher, R. A. and Yates, F. Statistical tables. London: Oliver and Boyd, 1938.