Zuzulova, Veronika, and Jaroslav Vido. “Normalized Difference Vegetation Index As a Tool for the Evaluation of Agricultural Drought in Slovakia”. Ecocycles 4, no. 1 (December 31, 2018): 83–87. Accessed June 25, 2021. https://www.ecocycles.net/ojs/index.php/ecocycles/article/view/124.