edited by William Ellet
Harvard Business School Publishing, 1997
Buku Referensi
Burton, Graeme, author
McGraw-Hill, 2010
Buku Teks
Fuchs, Christian, author
Sage Publications, 2014
eBooks
Ruth Colvin Clark
ASTD Press, 2010
Buku Teks
Clark, Ruth Colvin, author
VA ATD Press, 2015
Buku Teks