Humprey, Nicholas
New York Springer-Verlag , 1999
Buku Teks SO
Ali Nina Liche Seniati
Fakultas Psikologi Universitas Indonesia, 1997
UI - Laporan Penelitian
Blackwell Publishers, 1995
Buku Teks
Highet, Gilbert
Columbia University Press, 1954
Buku Teks
Santrock, John W.
W.C. Brown Publisher, 1991
Buku Referensi