T. Rajasivaranjan, N.R. Patel, A. Ponraj, V. Kumar, and U. Surendran. “Development and Application of SPI Generator Using Open Source for Analyzing Drought at a Varying Time Scale”. Journal of Agrometeorology, vol. 21, no. 4, Dec. 2019, pp. 420-6, doi:10.54386/jam.v21i4.276.