Millard, Elaine
Open University Press, 1994
Buku Teks
Payne, Elaine
Prentice-Hall, 2000
Buku Teks
Jacobs, Jennifer, author
Editions Didier Millet, 2011
Buku Referensi
Bramer, George R., author
Charles E. Merrill Publishing Company, 1981
Buku Teks
Greendwood, Jean, author
Oxford Oxford University Press, 1988
Buku Teks