1. Arrington, R. E. Time-sampling studies of child behavior.Psychol. Monog., 1939,51, No. 228, 3–193.
2. Craig, A. T. On the distributions of certain statistics.Amer. J. Math. 1932,54, 353–366.
3. Dudycha, G. J. An objective study of punctuality in relation to personality and achievement.Arch. Psychol., 1936,29, No. 204, 1–53.
4. Irwin, J. O. On the frequency distribution of the means of samples from a population having any law of frequency with finite moments, with special reference to Pearson's Type II.Biometrika, 1927,19, 225–239.
5. Kenney, J. F. Mathematics of statistics, Part Two. 1939. New York: D. Van Nostrand Co. Pp. 202.