Humphries, john, author
Glorier International, 1999
Buku Referensi
American Society for Training and Development Research
American Society for Training & Development, 2012
eBooks
Elaine Biech, editor
American Management Association, 2008
eBooks
Ichsan Malik, author
TIFA, 2007
Buku Teks
Lykins, Lorrie, author
American Society for Training & Development, 2011
eBooks