1. Davidson, R. and MacKinnon., J.G. 1993.Estimation and Inference in Econometrics, 874New York: Oxford University Press.
2. EHNRI (Ethiopian Health and Nutrition Research Institute). 1997.Food Composition Tables for Use in EthiopiaPart III, 34Addis Ababa, Ethiopia: EHNRI.
3. Agriculture for Consumers: Experiences from Norway
4. Gujarati, D.N. 1995.Basic Econometrics., 2nd, 705New York: McGraw-Hill International Editions.