Source: Data from Patterson, H. D., and H. L. Lucas. 1962. Change-over designs. Technical Bulletin 147, North Carolina Agricultural Experiment Station and the USDA.  Reproduced in Ratkowsky, D. A., M. A. Evans, and J. R. Alldredge. 1993. Cross-over Experiments: Design, Analysis, and Application. New York: Dekker.