Moore, John A., author
Macmillan, 1985
Buku Teks
Sorauf
Little, Brown and Company, 1980
Buku Teks
Burns, James McGregor, author
Prentice-Hall, 1963
Buku Teks
CQ Press, 2003
Buku Teks
Bailey, Stephen K., author
Voice of America Forum Lectures, 1956
Buku Teks