Leder, Malcolm
Longman Group, 1991
Buku Teks
Leder, Malcolm
Pitman, 1991
Buku Teks
London : Consumers association and hodder & stoughton, 1989, 1989
Buku Referensi
Borrie, Gordon, author
Penguin Books, 1976
Buku Teks
Mickelburgh, John
Profesional Books, 1979
Buku Teks