Ramsay, Michael C.
John Wiley & Sons, 2002
Buku Teks SO
Simeonsson, Rune J.
Allyn and Bacon, 1986
Buku Teks SO
edited by Ronald J. Prinz
Jessica Kingsley, 1991
Buku Referensi
Lidz, Carol Schneider
John Wiley & Sons, 2003
Buku Teks SO
Robinson, Dana Gaines
American Society for Training & Development Press, 2000
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