1. MDM (2009) Manual for Drought Management, Report of Department of Agriculture and Cooperation, Ministry of Agriculture Government of India New Delhi, November 2009
2. WMO (2012) Standardized Precipitation Index User Guide, Report of World Meteorological Organization (M. Svoboda, M. Hayes and D. Wood), Geneva, ISBN 978-92-63-11091
3. Mckee TB, Doesken NJ, Kleist JR (1993) The relationship of drought frequency and duration to time scales. In: 8th conference on applied climatology, Anaheim, California, 17–22 January, pp 179–184
4. Zarei and Eslamian (2017) Trend assessment of precipitation and drought index (SPI) using parametric and non-parametric trend analysis methods (case study: arid regions of southern Iran). Int J Hydrol Sci Technol 7(1):12–38. https://doi.org/10.1504/IJHST.2017.080957
5. Incoom (2020) Rainfall variabilities and droughts in the Savannah zone of Ghana from 1960–2015. Sci Afr. https://doi.org/10.1016/j.sciaf.2020.e00571