Gleeson, Simon, author
Oxford University Press, 2012
Buku Teks
editor, Brian J. Terry
Toppan Company, 1997
Buku Referensi
Barger, Harold, author
Rand McNally, 1969
Buku Teks
Cencini, Alvaro
Routledge , 1997
Buku Teks
International Monetary Fund , 1983
Buku Teks