Humphries, john
Groiler International, 1993
Buku Teks
Humphries, john, author
Glorier International, 1999
Buku Referensi
McLeod, Doug, author
[American Management Association;, ], 2010
eBooks
Stewart, Grant
Erlangga , 1995
Buku Teks
Voe, Merrill De
Prentice-Hall, 1957
Buku Teks