Royal Tropical Institut (KIT) , 1991-1992
Buku Referensi
Henderson, David, author
New Zealand Business Roundtable , 1998
Buku Teks
Tremblay, Victor J., author
[Springer, ], 2012
eBooks
Longman , 1999
Buku Teks
Choi, Bae-geun, author
Pakyoungsa, 2007
Buku Teks