Porter-O`Grady, Tim, author
Mosby, 1998
Buku Teks
Barker, Carol, author
Sage Publications, 1996
Buku Teks
Charles Webster
Open University Press, 2001
Buku Teks
Oxford University Press, 1979
Buku Teks
Stamatis, Diomidis H.
Chicago Irwin 1996 , 1996
Buku Teks