1. Bales, R. F. (1958). Task roles and social roles in problem-solving groups. In E. E. Maccoby, T. M. Newcomb & I. Hartley (Eds.),Readings in social psychology. New York: Holt, Rinehart & Winston.
2. Beck, A. P. (1974). Phases in the development of structure in therapy and encounter groups. In D. Wexler & L. N. Rice (Eds.),Innovations in client-centered therapy. New York: Wiley Interscience.
3. Beck, A. P. (1981a). Developmental characteristics of the system forming process. In J. Durkin (Ed.),Living groups: Group psychotherapy and general system theory. New York: Brunner-Mazel.
4. Beck, A. P. (1981b). The study of group phase development and emergent leadership.Group, 5(4), 48?54.
5. Beck, A. P., Brusa, J. A., & Stone, M. (1989). Designing a sociometric measure of emergent leadership. Paper presented at the 10th International Congress of Group Psychotherapy, Amsterdam.