Johnson, D. W., & Johnson, F. P. (1982). Joining together: Group theory and group skills (2nd.ed.). Prentice-Hall.

Johnson, David W., and Frank P. Johnson. Joining Together: Group Theory and Group Skills. 2nd.ed. New Jersey: Prentice-Hall, 1982.

Johnson, David W., and Frank P. Johnson. Joining Together: Group Theory and Group Skills. 2nd.ed. Prentice-Hall, 1982.