Swallow, Lisa
Wiley Publishing, Inc., 2009
Buku Teks
edited by Roodney A. Ellis
Routledge, Taylor & Francis Group, 2009
Buku Teks
Butterworth-Heinemann, 1993
Buku Teks
edited by Ron Zemke and John A. Woods
American Management Association, 1998
eBooks
Andres, Cameron K.
Prentice-Hall, 1998
Buku Teks