Margareth Edith, author
Fakultas Psikologi Universitas Indonesia, 1991
UI - Skripsi (Membership)
Fisher, Bruce, author
Grasindo, 2003
Buku Teks
[publisher not identified], [date of publication not identified]
Naskah
Powell, Gary N.
Sage Publications, 1988
Buku Teks
Sembiring Pandia, Weny Savitri, author
1997
UI - Skripsi (Membership)