Fischer, G., Shah, M.M., Kassam, A.H., & van Velthuizen, H.T. (1994). Agro-Ecological Land Resources Assessment for Agricultural Development Planning: A Case Study for Kenya. Resources Data Base and Land Productivity: Technical Annex 8: Crop Productivity Assessment: Results at District Level. XQ-94-805 , IIASA, Laxenburg, Austria.