Steel, R. G., & Torrie, J. H. (1980). Principles and procedures of statistics: A biometrical approach (2nd ed.). McGraw-Hill, Inc..

Steel, Robert G.D, and James H. Torrie. Principles and Procedures of Statistics: A Biometrical Approach. 2nd ed. New york: McGraw-Hill, Inc., 1980.

Steel, Robert G.D, and James H. Torrie. Principles and Procedures of Statistics: A Biometrical Approach. 2nd ed. McGraw-Hill, Inc., 1980.