Brock, Dee, author
John Wiley & Sons, 1978
Buku Teks
Feldman, Richard, author
Prentice-Hall, 1999
Buku Teks
Santayana, George, author
Columbia University Press, 1995
Buku Teks
Hope, A. D., author
Melbourne University Press, 1985.
Buku Teks
Peacocke, Christopher
clarendon Press, 2007
Buku Teks