Brokings Institution, 1950
Buku Teks
Brookings institution, 1949
Buku Teks
Mangone, Gerard J., author
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., author
Prentice-Hall, 1965
Buku Teks