Freund, J. E., Williams, F. J., & Perles, B. M. (1988). Elementary business statistics: The modern approach (Fifth edition.). Prentice Hall.

Freund, John E., Frank Jefferson Williams, and Benjamin M. Perles. Elementary Business Statistics: The Modern Approach. Fifth edition. Englewood Cliffs, N.J.: Prentice Hall, 1988.

Freund, John E., et al. Elementary Business Statistics: The Modern Approach. Fifth edition. Prentice Hall, 1988.