Thorndike, Edward Lee
Harvard University Press, 1943
Buku Teks
Herskovits, Melville J. (Melville Jean), 1895-1963, author
Alfred A. Knopf, 1967
Buku Teks
Erikson, Erik H.
W.W Norton and Company, 1958
Buku Teks
Highet, Gilbert, author
Columbia University Press, 1954
Buku Teks
George Allen and Unwin, 1956
Buku Teks