Brookings institution, 1949
Buku Teks
Mangone, Gerard J.
Syracuse University Press, 1962
Buku Teks
edited by Robert W. Tucker, Charles B. Keely, and Linda Wrigley
Westview Press, 1990
Buku Teks
Pratt, Julius W.
Prentice-Hall, 1965
Buku Teks
Schaller, Michael
Oxford University press, 1979
Buku Teks