Banner, Michael
Cambridge Unuversity Press , 1999
Buku Teks
Tiles, J.E., author
Routledge, 2000
Buku Teks
Wilkins, Lee, author
Lawrence Erlabum Associates, 2005
Buku Teks
Pojman, Louis P., author
New York : Oxford University Press, 2000
Buku Teks
Smith, Michael, author
Cambridge University Press , 2004
Buku Teks