Johnson, David W., 1940-
Joining together : group theory and group skills
Allyn and Bacon, 2000
 Buku Teks
Johnson, David W., 1940-
Joining together : group theory and group skills
Pearson Education, 2006
 Buku Teks
Johnson, David W., 1940-
Joining together : group theory and group skills
Pearson, 2014
 Buku Teks
Johnson, David W., 1940-
Joining together : group theory and group skills
Pearson, 2017
 Buku Teks
Group dynamics: research and theory
edited by Dorwin Cartwright, Alvin Zander
Harper & Row , 1968
 Buku Teks SO