Boner, Roger Alan, author
World Bank, 1993
Buku Teks
Schlesinger, Rudolf B.
The Foundation Press, 1950
Buku Teks
Morris, J.H.C.
At The Clarendon Press, 1960
Buku Teks
Kauper, Paul G., author
Little, Brown, 1971
Buku Teks
Keir, D. L. (David Lindsay), author
Oxford University Press, 1948
Buku Teks