David Boucher, Paul Kelly, editor
Oxford Univesity Press, 2009
Buku Teks
Ebenstein, William, author
Thomson Learning, 2000
Buku Teks
Ebenstein, William, author
Rinehart, 1960
Buku Teks
Rivkin, Malcolm D., author
Frederick A. Praeger, 1965
Buku Teks
Gill, Richard T. (Richard Thomas), 1927-2010, author
Prentice-Hall, 1963, 1967
Buku Teks