1. Morales, Chorister (1977). Rainfall Variability: A Natural Phenomenon. Ambio, Vol. 6, No.1, Water: A Special Issue (1977), pp. 30-33
2. Gregory, S. (1989). The Changing Frequency of Drought in India, 1871-1985 .The Geographical Journal, Vol. 155, No. 3 (Nov., 1989), pp. 322-33
3. Bagla, Pallava. (2002). Drought Exposes Cracks in India's Monsoon Model. Science, New Series, Vol. 297, No. 5585 (Aug. 23, 2002), pp. 1265-1267
4. Rangaswami, Amrita (1974). The Uses of ‘Drought’. Economic and Political Weekly, Vol. 9, No. 50 (Dec. 14, 1974), pp. 2069+2071-2074
5. Ratcliffe, Miles, Rydz and Shaw. (1978). Meteorological Aspects of the 1975-76 Drought [and Discussion] . Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Vol. 363, No. 1712 (Nov. 1, 1978), pp. 3-20
6. Hulme, Mike (1990). The Changing Rainfall Resources of Sudan .Transactions of theInstitute of British Geographers. New Series, Vol. 15, No. 1 (1990), pp. 21-34
7. Walsh, Hulme and Campbell. (1998). Recent Rainfall Changes and Their Impact on Hydrology and Water Supply in the Semi- Arid Zone of the Sudan. The Geographical Journal, Vol. 154, No. 2 (Jul., 1988), pp. 181-197
8. Skaggs, Richard H. (1975). Drought in the United States, 1931-40. Annals of the Association of American Geographers, Vol. 65, No. 3 (Sep., 1975), pp. 391-402