Niles, Mary Cushing
Harper & Brothers, 1940
Buku Teks
Frohman, Alan L.
McGraw-Hill, 1992
Buku Teks
McDermott, Lynda Caryl
Prentice-Hall, 1992
Buku Teks
Dew, R. Beresford
Wiley, 1973
Buku Teks
Haneberg, Lisa
American Society for Training & Development, 2011
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