Battersby, Albert
Penguin Books, 1968
Buku Teks
Sugars, Bradley J.
McGraw-HIll , 2006
Buku Teks
Storholm, Gordon R.
Prentice-Hall, 1982
Buku Teks
Still, Richard R.
Prentice Hall International, 1988
Buku Teks
Mikula, Jim
American Society for Training and Development Press;, 2004
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