Keegan, John, author
Routledge, 1996
Buku Referensi
Hardy, W.G.
Schenkman Publishing Company Inc., 1962.
Buku Teks
edited by John Parker
Pitman, 1952
Buku Referensi
editor, John R. Hinnells
Macmillan, 1993
Buku Referensi
Tomlinson, R.A., author
British Museum Press, 1995
Buku Teks