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Agricultural Development Council , 1969
Buku Teks
Winter, Michael, author
Routledge, 1996
Buku Teks
Hall, C.J.
A. & C. Black, 1924
Buku Teks
Hardin, Charles M., author
Free Press, 1952
Buku Teks
National Research Institute of Agricultural Economic, Ministry of Agriculture, Forestry and Fisheries , 2000
Buku Teks