Heath, Eric
Prentice-Hall, 1953
Buku Teks
Tobias, Ronald B.
Writer's Digest Books, 1997
Buku Teks
Tompkins, Al
CQ Press, 2012
Buku Teks
Mason, Elizabeth J.
John Wiley & Sons, 1978
Buku Teks
Vassallo, Philip
[American Management Association;, ], 2010
eBooks