Dhaif Allah, A. A., and N. Md. Hashim. “Analysis of Meteorological Drought in Tihama Plain, Yemen Using Standardized Precipitation Index (SPI)”. GEOGRAFI, vol. 4, no. 2, Oct. 2016, pp. 9-20, https://ojs.upsi.edu.my/index.php/GEOG/article/view/1930.