Seton-Watson, R.W., author
Norton, 1972
Buku Teks
Millard, Thomas F., author
Century, 1916
Buku Teks
Bell, Frederic Gladstone
E & FN Spon, 1993
Buku Teks
Goody, Esther N
Cambridge University Press, 1978
Buku Teks
Foley, Gerald, author
Penguin Books, 1976
Buku Teks