Rossum, Ralph A., author
Lexington Books, 2001
Buku Teks
Rehnquist, William H.
William morrow and company,inc., 1987
Buku Teks
Johnson, Gerald W., author
William Morrow and Company, 1962
Buku Teks
edited by Burke Marshall
United States International Communication Agency, 1982
Buku Teks
Scigliano, Robert
The Free Press, 1971
Buku Teks