Levitin, Daniel J.
Dutton, 2006
Buku Teks
Lucas, Bob
American Management Association, 2008
eBooks
edited by J. Graham Beaumont
Grange Books, 1989
Buku Referensi
Brogan, Kelly
Thorson, 2016
Buku Teks
Verhaeghen, Paul
Oxford University Press, 2017
eBooks