Medhurst, David, author
Blackwell Scientific Publications, 1994
Buku Referensi
Akester, Patricia, author
Sweet & Maxwel, [Date of publication not identified]
Buku Teks
Shilling, Dana, author
Prentice-Hall, 1998
Buku Referensi
Barrow, Colin, author
John Wiley & Sons, 2001
Buku Teks
Nicholson, Max, author
Penguin Books, 1970
Buku Teks