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Dyfyniad Arddull ChicagoEpp, Donald J. Introduction to Agricultural Economics. New York: Collier Macmillan, 1981.
Dyfyniad MLAEpp, Donald J. Introduction to Agricultural Economics. New York: Collier Macmillan, 1981.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.