United Nations Environment Programme
Nettlap, 1993
Buku Referensi
Charney, Cyril, author
American Management Association, 2006
eBooks
Harvard Business School Press, 2004
Buku Teks
Topchik, Gary S., author
[American Management Association;, ], 2004
eBooks
Williams, Kate
MacMillan Press , 1989
Buku Teks