National Council of Farmer Cooperatives , 1992
Buku Teks
edited by Gary Hoover, Alta Campbell, Patrick Spain
The Reference Press, 1991
Buku Referensi
Voorhis, Jerry
Harper & Row, 1961
Buku Teks
Kislev, Yoav, author
World Bank, 1989
Buku Teks
De Leon, Hector S., author
Central Lawbook, 1975
Buku Teks