Hill, G.A., author
Ginn, 1889
Buku Teks
Worth, Thomas, author
Prentice-Hall of India 1981, 1977
Buku Teks
Buick, Joanna, author
Icon Books, 1995
Buku Teks
Gordon, W. Terrence, author
Writer and Readers Pubishing, 1996
Buku Teks
Carpenter, Catrine, author
McGraw-Hill, 2004
Buku Teks