The World Bank, 2007
Buku Teks
Wold Bank, 2004
Buku Teks
Price Waterhouse, 1966
Buku Teks
Mueller, Rudolf
Fritz Knapp Verlag, 1972
Buku Teks
editors and contributors, Joseph J. Norton, Thomas L. Bloodworth ; editorial coordinator, Terry K. Pennington
Martinus Nijhoff Publishers, 1995
Buku Teks