Shaughnessy, John J., author
McGraw-Hill, 2006
Buku Teks
Giles, David C., author
Routledge, 2002
Buku Teks
Barker, Chris, author
John Wiley & Sons, 1994
Buku Teks
Zechmeister, Eugene B., author
McGraw-Hill, 1992
Buku Teks
bt Peter Banister ... [and others]
Open University Press, 2006
Buku Teks