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Buku Referensi
Routledge, 2000
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edited by W. Gellert, S. Gottwald, M. Hellwich, H. Kastner, H. Kustner
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Buku Referensi
Ensminger, Audrey; Ensminger, M.E.; Konlande, James E.; Robson, John R.K.
CRC Press, 1994
Buku Referensi
Ahluwalia, V.K., author
Taylor and Francis, 2008
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