Schwelb, Egon
Quadrangle, 1964
Buku Teks
Ries, Al, author
Binapura Aksara, 2001
Buku Teks
Universitas Indonesia, 1992
UI - Skripsi (Membership)
Nickel, James W., author
Gramedia Pustaka Utama, 1996
Buku Teks
Mortensen, Kurt W., author
American Management Association, 2004
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