DSA (2006): "Study on Improving the Efficiency of Input Market: Volume 1," Addis Ababa: Development Studies Associates.

- Duan, N., W. Manning, C. Morris, and J. Newhouse (1984): "Choosing between the Sample Selection Model and the Multi-Part Model," _Journal of Business & Economic Statistics_ 2(3), 283-289.

- EEA/EEPRI (Ethiopian Economic Association/ Ethiopia Economic Policy Research Institute) (2006): Evaluation of the Ethiopian Agricultural Extension with Particular Emphasis on the Participatory Demonstration and Training Extension System (PADETES). Addis Ababa, Ethiopia.

- Fafchamps, M., and A. R. Quisumbing (1999): "Human Capital, Productivity, and Labor Allocation in Rural Pakistan," _The Journal of Human Resources_ 34(2), 369-406.

- Feder, G., R. E. Just, and D. Zilberman (1985): "Adoption of Agricultural Innovations in Developing Countries: A Survey," _Economic Development and Cultural Change_ , 33(2), 255-298.

- Feder, G., and D.L. Umali (1993): “The Adoption of Agricultural Innovations: a Review. _Technological Forecasting and Social Change_ , 43: 215-239.

- Fufa, B., and R. Hassan (2006): "Determinants of Fertilizer Use on Maize in Eastern Ethiopia: A Weighted Endogenous Sampling Analysis of the Extent and Intensity of Adoption," _Agreko_ , 45, 38-49.

- Gebremedhin, B., D. Hoekstra, and A. Tegegne (2006): "Commercialization of Ethiopian Agriculture: Extension Service from Input Supplier to Knowledge Broker and Facilitator," _International Livestock Research Institute, IPMS Working Paper_ , 1.

Greene, W. H. (2007): _Limdep Version 9.0 Econometric Modeling Guide_ . New York: Econometric Software, Inc.

- Gregory, D. I., Bumb, B. L., 2006. Factors affecting the supply of fertilizer in Sub-Saharan Africa. Agriculture and Rural Development Discussion Paper 24, Washington, World Bank.

- Heisey, Paul W. and George Norton (2007). “Fertilizers and other farm chemicals” in Robert Evenson and Prabhu Pingali (eds.) Handbook of Agricultural Economics, Amsterdam, Elsevier.

- Henao, J., and C. Baanante. 2006. Agricultural production and soil nutrient mining in Africa: Implications for resource conservation and policy development. IFDC, Muscle Shoals, AL.

- Honore, B. E., and E. Kyriazidou (2000): "Panel Data Discrete Choice Models with Lagged Dependent Variables," _Econometrica_ , 68, 839-874

- Howard, Julie, Eric Crawford, Valerie Kelly, Mulat Demeke, and José Jaime Jeje (2003) “Promoting highinput maize technologies in Africa: the Sasakawa-Global 2000 experience in Ethiopia and Mozambique” Food Policy 28: 335-248.

- Jayne, T. S., J. Govereh, M. Wanzala, M. Demeke (2003): “Fertilizer Market Development: A Comparative Analysis of Ethiopia, Kenya, and Zambia,” _Food Policy_ 28, 293-316.

- Jayne, T., T. Yamano, J. Nyoro (2004). “Interlinked Credit and Farm Intensification: Evidence from Kenya.” _Agricultural Economics_ 31, 209-18.

Kyriazidou, E. (1997): "Estimation of a Panel Data Sample Selection Model " _Econometrica_ , 65, 1335-1364 Larson, D.F., J.R. Anderson and P. Varangis (2004). "Policies on Managing Risk in Agricultural Markets," _World Bank Research Observer_ 19, 199-230.

- Larson, D.F. and F. Plessmann (2009). “Do farmers choose to be inefficient? Evidence from Bicol,” _Journal of Development Economics_ 90(1), 24-32.

- Marenya, Paswel P. and Christopher B Barrett (2009).  Soil Quality and Fertilizer Use Rates among Smallholder Farmers in Western Kenya,” Agricultural Economics 40(5), 561-72.

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