Snow, Peter G.
Holt, Rinehart and Winston, INC, 1967
Buku Teks
Joseph Maier, Richard W.Weatherhead
F. A. Praeger, 1964
Buku Teks
edited by David Collier
Princeton University Press, 1979
Buku Teks
Pierson, William W., author
D. Van Nostrand, 1953
Buku Teks
edited by Howard J. Wiarda, Harvey F. Kline
Westview Press, 2007
Buku Teks