Gadgil, Madhav
Routledge , 1995
Buku Teks
Chacko, Kollenparampil C.
Vora & Co. Publishers Private Ltd. , 1957
Buku Teks
Bauer, P.T.
Frederick A. Praeger, 1961
Buku Teks
Ballantine, Joseph W.
Brookings Institution Press, 1952
Buku Teks SO
Gupta, Anand P.
McGraw-Hill, 1977
Buku Teks