Mudd, Norma
Hodder & Stoughton Educational , 1998
Buku Teks
Blundell, Jon, author
Oxford University Press, 1982
Buku Teks
Gerber, Philip L., author
Random House, 1959
Buku Teks
Burton, Samuel Holroyd, author
Macmillan, 1995
Buku Teks
Coxon, Rosemary, author
Letts Educational, 1994
Buku Teks