Winick, Charles
Littlefield, Adams & Co., 1961
Buku Referensi
Ember, Carol R.
Prentice-Hall, 1985
Buku Teks SO
Haviland, William A.
Rinehart and Winston, 1974
Buku Teks SO
edited by Allan H. Smith and John L. Fischer
Prentice-Hall, 1970
Buku Teks SO
London: Tiger Books International, 1994,
Buku Referensi