McDonagh, Eileen L.
Oxford University Press, 1996
Buku Teks
Farr, Douglas, author
John Wiley & Sons, 2008
Buku Teks
Gray, Charles L.
The University of Michigan Press, 1988
Buku Teks
Cohen, Saul B.
Vioce of America Forum Lectures , 1968
Buku Teks
Levitan, Sar A.
Harper & Row , 1982
Buku Teks