Potten, A.J. van, author
Rabobank International Group, 1966
Buku Teks
Brelih, Miloš.
Jugoslavija,, 1960.
Buku Teks
Meenakshi, J.V., author
Department of Agricultural Economics , 1986
Buku Teks
edited by Robert J. Lawrie
McGraw-Hill, 1987
Buku Referensi
Prentis, J. M.
Halsted Press, 1980
Buku Teks