Nye, Joseph S., author
Pearson, 2012
Buku Teks
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Longman, 1991
Buku Referensi
Macmillan, 1991
Buku Teks
Snow, Edgar, author
Random House , 1962.
Buku Teks
Drucker, Peter F. (Peter Ferdinand), 1909-2005, author
Heinemann Profesional , 1990
Buku Teks