Karah, W., K., E.B., M., G.(1990).System approaches for improvement in agriculture and resource management / Kathleen K. Wilson, George E.B. Morren, Jr. .New York:Macmillan.
Gaya MLA
Wilson, Kathleen, Karah., Morren, George, E.B.."System approaches for improvement in agriculture and resource management / Kathleen K. Wilson, George E.B. Morren, Jr.".New York:Macmillan,1990.Textbook.