Poissant, Charles-Albert
Pustaka Tangga, 1993
Buku Teks
Robbins, Anthony
A Freeside Book, 1991
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Maxwell, John C., author
Harvest Publication House, 1997
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Maltz, Maxwell, 1899-1975, author
Interaksara, 2004
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Covey, Stephen R., author
Dunamis, 2015
Buku Teks