Farrar, Harry, author
The Donnington Press, 1970
Buku Teks
Hill, Christopher, author
LLP, 2003
Buku Teks
Oxford University Press, 2009
Buku Referensi
Cremona, Marise, author
Macmillan, 1989
Buku Teks
Smith, J. C. (John Cyril), author
Butterworth, 1992
Buku Teks