Artikel Jurnal
Porter, Hal, 1911-1984, author
Rigby, 1971
Buku Teks
Sandel, Michael J., author
Farrar, Staus and Giroux, 2010
Buku Teks
Drew, John
Butterworth, 1983
Buku Teks
Crittendon, Robert, author
[American Management Association;, ], 2002
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