Stern, Alfred
Arco Publishing, Inc., 1984
Buku Teks
Jane, author
HarperCollins, 2005
Buku Teks
Mackenizie, John
Illinois: Dow Jones-Irwin, 1989
Buku Teks
Foster, Lynn
West Publishing Company, 1983
Buku Teks
Rawls, John
Harvard University Press, 2003
Buku Teks