Gombas, Pal
Pergamon Press, 1973
Buku Teks SO
Ida Irma Pratitia R.
Fakultas Psikologi Universitas Indonesia, 2005
UI - Tesis Membership
Khaled Khalaf, Vojkan Vidojkovic, John R. Long, Piet Wambacq
Springer Nature, 2019
eBooks
Crain, William C
Prentice-Hall, 2005
Buku Teks SO
Lewis, Stephen
Oxford University Press, 1984
Buku Teks SO