Hopfe, Lewis M.
Prentice-Hall, 1998
Buku Teks
edited by Stewart Sutherland, Leslie Houlden, Peter Clarke, Friedhelm Hardy
Routledge, 1988
Buku Referensi
Longman Current Affairs, 1992
Buku Teks
Bettany, G.T., author
Bracken Books, [date of publication not identified]
Buku Referensi
consulting editor, Wendy Doniger
Encyclopaedia Britannica, Inc., 2006
Buku Referensi