Steers, R. M., Porter, L. W., & Biglley, G. A. (1996). Motivations and leardership at work (6th ed.). Mac Graw hill.

Steers, Richard M., Lyman W. Porter, and Gregary A. Biglley. Motivations and Leardership at Work. 6th ed. New York: Mac Graw hill, 1996.

Steers, Richard M., et al. Motivations and Leardership at Work. 6th ed. Mac Graw hill, 1996.