Estrada, Rafael R.
Central Book Supply,Inc., 1973
Buku Teks
Still, Richard R
Prentice Hall International, 1988
Buku Teks
Ohai, Tim, author
American Society for Training & Development, 2008
eBooks
Battersby, Albert, author
Penguin Books, 1968
Buku Teks
Sugars, Bradley J., author
McGraw-HIll , 2006
Buku Teks