Neustadt, Richard E., author
John Wiley & Sons, 1961
Buku Teks
Baldacci, David
Warner Books, 1996
Buku Teks
Dominguez, John R.
Lexington Books , 1974
Buku Teks
Duffus, R.L, author
Alfred A. Knopf, 1928
Buku Teks
Jamieson, Kathleen Hall
Oxford University Press, 1992
Buku Teks