Hogshead, Sally, author
Harper Business, 2016
Buku Teks
Hand, Amy, author
American Society for Training & Development, 2010
eBooks
Elliot, Rose, author
Chapmans Publisher Ltd., 1994
Buku Referensi
Minrath, William R., author
D. Van Nostrand, 1956
Buku Teks
Doucett, Elisabeth, author
[American Management Association, ], 2008
eBooks