1. Africa Watch (1991) Evil days: 30 years of war and famine in Ethiopia. Africa Watch Rep.
https://www.hrw.org/sites/default/files/reports/Ethiopia919.pdf
2. Akinremi OO, McGinn SM, Barr AG (1996) Evaluation of the Palmer Drought Index on the Canadian prairies. J Clim 9:897–905
3. Allen RG, Pereira LS, Raes D, Smith M (1998) Crop evapotranspiration (guidelines for computing crop water requirements). Food and Agriculture Organization of the United Nations Irrigation and Drainage Paper 56
4. Beck C, Grieser J, Rudolf B (2004) A new monthly precipitation climatology for the global land areas for the period 1951 to 2000 (published in Climate Status Report 2004, pp. 181–190, German Weather Service, Offenbach, Germany)
5. Bhalme HN, Mooley DA (1979) On the performance of modified Palmer index. In: Proceedings of international symposium on hydrological aspect of droughts, vol. 1. New Delhi, UNESCO, pp 373–383