Johnson, D. W., & Johnson, R. T. (1991). Learning together and alone: Cooperative, competitive, and individualistic learning (Third edition.). Allyn and Bacon ; Prentice-hall, Inc..

Johnson, David W., and Roger T. Johnson. Learning Together and Alone: Cooperative, Competitive, and Individualistic Learning. Third edition. Boston: Allyn and Bacon ; Prentice-hall, Inc., 1991.

Johnson, David W., and Roger T. Johnson. Learning Together and Alone: Cooperative, Competitive, and Individualistic Learning. Third edition. Allyn and Bacon ; Prentice-hall, Inc., 1991.