Smith, D. N.
Clarendom Press, 1951
Buku Teks
Oxford University Press , 1988
Buku Teks
Ritter, Lawrence S., author
Basic Books, 1970
Buku Teks
Christensen, Mary, 1951- , author
American Management Association, 2007
eBooks
Ennico, Cliff, author
American Management Association, 2008
eBooks