Keller, G., Bartel, H., & Warrack, B. (1994). Statistics for management and Economics (3rd. ed.). Duxbury.

Keller, Gerald, Henry Bartel, and Brian Warrack. Statistics for Management and Economics. 3rd. ed. Belmont: Duxbury, 1994.

Keller, Gerald, et al. Statistics for Management and Economics. 3rd. ed. Duxbury, 1994.