Busch, H. Ted
Macmillan, 1980
Buku Teks
Meijer, Maarten, author
Seoul Hyeonamsa 2005
Buku Teks
Brenda Rapp
Psychology Press, 2001
Buku Teks
Williams, Albert N.
Association Press, 1959
Buku Teks
Phillips, Jack J., author
American Society for Training & Development, 2009
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