Howell, J. P., & Costley, D. L. (2006). Understanding behaviors for effective leadership (2nd ed.). Pearson/Prentice Hall.

Howell, Jon P., and Dan L. Costley. Understanding Behaviors for Effective Leadership. 2nd ed. Upper Saddle River, N.J. ; New Delhi: Pearson/Prentice Hall, 2006.

Howell, Jon P., and Dan L. Costley. Understanding Behaviors for Effective Leadership. 2nd ed. Pearson/Prentice Hall, 2006.