Christie, Agatha, 1890-1976, author
Gramedia Pustaka Utama, 2017
Buku Teks
Jakarta : PT. Reka Gagas Cipta, 2006,
Majalah, Jurnal, Buletin
Asmadi
Indira, 1980
Buku Teks
Sarlito Wirawan Sarwono, author
Salemba Humanika, 2009
Buku Teks
Faurot, Kimberly K., author
[American Management Association, ], 2009
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