Ferguson, Nicolas, author
Evans Brothers Limited, 1981
Buku Teks
The World Bank, 1996
Buku Referensi
McGovern, John
Prentice Hall International, 1987
Buku Teks
Tomasowa, Francien Herlen, author
Universitas Brawijaya , 2005
Buku Teks
Eckersley, C. E. (Charles Ewart), 1892-1967, author
Longmans, Green and Co., 1953
Buku Referensi