Christensen, Larry B., 1941-, author
Boston Allyn and Bacon 1988,
Buku Referensi
Christensen, Larry B., 1941-, author
Pearson/Allyn & Bacon, 2007
Buku Teks
Tobing, Christina Ruth Elisabeth Lumbang, author; Junita Elvira Pandji Surya, author
Fakultas Psikologi Universitas Indonesia, 2004
UI - Tesis Membership
Hairston, Nelson G., author
Cambridge University Press, 1994
Buku Teks
UI - Tesis Membership