Phythian, B. A.
Hodder & Stoughton, 1993
Buku Referensi
Brewer, E. Cobham
New York, Harper Brothers
Buku Referensi
revised by Ivor H. Evans
Cassell & Company, 1975
Buku Referensi
Shaw, Bernard, 1856-1950
Penguin Books , 1951
Buku Teks
Roberts, Russell D.
Pearson Prentice Hall, 2007
Buku Teks