Gajanan H. Chavhan, Mangesh S. Deshpande, Rajesh M. Jalnekar. “A Comprehensive Investigation of Drought and Standard Precipitation Index (SPI)”. Mathematical Statistician and Engineering Applications 70, no. 2 (January 14, 2023): 419–432. Accessed July 3, 2024. https://philstat.org/index.php/MSEA/article/view/1646.