Nelson, Carl A.
Import export : how to get started in international trade / Carl A. Nelson
McGraw-Hill, 2000
 Buku Teks SO
Handbook of world families
edited by Bert N. Adams, Jan Trost
Sage Publications, 2005
 Buku Referensi
Caves, Richard E.
World trade and payments : an introduction
Harper Collins College Publishers, 1996
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Das, Bhagirath Lal
The world trade organisation: a guide to the framework for international trade
Zed Books, 1999
 Buku Teks
Foster, Douglas
Travel and tourism management / Douglas Foster
Macmillan, 1985
 Buku Teks