Griffin, Ricky W.
Addison-Wesley, 1995
Buku Teks
The Society of Business Administration, Kwansei Gakuin University, 2009
Majalah, Jurnal, Buletin
Czinkota, Michael R.
The Dryden Press, 1992
Buku Teks
ITM Business School, 2008
Majalah, Jurnal, Buletin
Wormald, Avison
Pan Books, 1973
Buku Teks