William, J.E. HAll
Butterworth, 1970
Buku Teks
Rodd, Laurel Rasplica
University of Hawaii , 1980
Buku Teks
Gagne, Robert M.
Holt, Rinehart and Winston, 1962
Buku Teks
Walinsky, Louis J.
The Twentieth Century Fund, 1962
Buku Teks
University of Missouri Press, 1970
Buku Teks