Rowland, Diana, author
Bumi Aksara, 1992
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Langford, Beverly Y., author
American Management Association, 2005
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Chew, Sally
Times Books International, 1995
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Indah Mutiara Putri Fani, author
2019
UI - Tesis (Membership)
Hutabarat, Hermine E.P.
Gunung Mulia , 1998
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