References (PPLOT command)
Blom, G. 1958. Statistical estimates and transformed beta variables. New York: John Wiley and Sons.
Chambers, J. M., W. S. Cleveland, B. Kleiner, and P. A. Tukey. 1983. Graphical methods for data analysis. Boston: Duxbury Press.
Lehmann, E. L. 1975. Nonparametrics: Statistical methods based on ranks. San Francisco: Holden-Day.
Tukey, J. W. 1962. The future of data analysis. Annals of Mathematical Statistics, 33:22, 1-67.