Routledge, 1997
Buku Referensi
Czinkota, Michael R., author
The Dryden Press , 1996
Buku Teks
The Society of Business Administration, Kwansei Gakuin University, 2009
Majalah, Jurnal, Buletin
Griffin, Ricky W., author
Addison-Wesley, 1995
Buku Teks
ITM Business School, 2008
Majalah, Jurnal, Buletin