Balaam, David N., 1950-, author
Pearson/Prentice Hall, 2005
Buku Teks
Balaam, David N., 1950-, author
Prentice-Hall, 1996
Buku Teks
edited by W. Ladd Hollist
Westview Press, 1985
Buku Teks
Williamson, John
Basic Books, Inc., 1983
Buku Teks
Gill, Stephen, author
John Hopkins University Press, 1988
Buku Teks