Bannock, G., author
Allen Lane / The Viking Press, 1979
Buku Referensi
Whitten, D.G.A., 1921-, author
Penguin Books, 1972
Buku Referensi
Whittow, John B., author
Allen Lane, 1984
Buku Referensi
Penguin, 1998
Buku Referensi
Greener, Michael, author
Penguin books, 1994
Buku Referensi