Burnard, Philip, author
Chapman&Hall,, 1995
Buku Referensi
Curry, David A., author
Addison-Wesley, 1992
Buku Teks
Maxfield, Brent, author
Academic Press, 2014
eBooks
VNU Business Publications, 1989
Buku Referensi
Flynn, Peter, author
International Thomson , 1995
Buku Teks