Sengupta, R., and S. Zhukovskiy. “Ekeland’s Variational Principle for Functions Unbounded from below”. Discontinuity, Nonlinearity, and Complexity 9, no. 4 (August 17, 2026): 553–558. Accessed August 17, 2026. https://lhscientificpublishing.com/index.php/DNC/article/view/1801.