Held, Gilbert
John Wiley & Sons, 1995
Buku Referensi
Chabner, Davi-Ellen
W.B. saunders , 2001
Buku Teks
Schwartz, Robert J.
Crowell , 1955
Buku Referensi
Jones, David J.
Australia, Second Back Row Press
Buku Referensi
Oxford University Press, 1996
Buku Referensi