Seligman, C.G., author
Thornton Butterworth, 1939
Buku Teks
edited by Colin M. Turnbull
Kingsport Press, 1973
Buku Teks
Coughlan, Robert, author
Time Incorporated, 1962
Buku Teks
Fage, J.D., author
Routledge, 1995
Buku Teks
edited by Bisheshwar Prasad
Asia Public House, 1960
Buku Teks