Ryan, Damian, author
Kogan Page, 2016
Buku Teks
Collin, Jackie
Simon and Schuster , 1983
Buku Teks
Watts, Alan W., author
John Murray , 1948
Buku Teks
Axelrod, Alan, author
American Management Association, 2007
eBooks
Ringwood:Penguin Books, 1988
Buku Teks