James F. Sumeisey, author
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UI - Skripsi (Membership)
Vandewalle, Dirk
I.B. Tauris Publishers , 1998
Buku Teks
Stocking, George W., author
Vanderbilt University Press, 1970
Buku Teks
Porter, Stanley P.
McGraw-Hill, 1965
Buku Teks
Johnston, Daniel
Penwell Books, 1994
Buku Teks