Humphries, john
Glorier International, 1999
Buku Referensi
McLeod, Doug
[American Management Association;, ], 2010
eBooks
Stewart, Grant
Erlangga , 1995
Buku Teks
Voe, Merrill De
Prentice-Hall, 1957
Buku Teks
Miller, William
American Management Association, 2009
eBooks