Zenger, John H., author
McGraw-Hill, 2004
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Maxwell, John C., author
NY : Center Street, 2014
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Mackoff, Barbara, author
American Management Association, 2001
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Zenger, John H., author
McGraw-Hill, 2003
Buku Teks
Sharma, Robin, author
Buana Ilmu Populer, 2006
Buku Teks