International development Research Centre, 1979
Buku Teks
Igbozurike, Martin
Scandinavian Institute of African Studies, 1976
Buku Teks
Manchester University Press, 1971
Buku Teks
National Research Institute of Agricultural Economic, Ministry of Agriculture, Forestry and Fisheries , 2000
Buku Teks
Institute of Southeast Asian Studies, 2007
Buku Teks