Kleinberger, Daniel S.
Little, Brown and Company, 1995
Buku Teks
by Rob Ranyard [and others]; edited by Rob Ranyard, W. Ray Crozier and Ola Svenson
Routledge , 1997
Buku Teks
Shoemaker, Donald J., author
Oxford Univesity Press, 2000
Buku Teks
Federal Publications, 1988
Buku Referensi
Brook, James
Little, Brown , 1994
Buku Teks