Fujita, Takaaki, Raed Hatamleh, and Ahmed Salem Heilat. “ContraSoft Set and ContraRough Set With Using Upside-down Logic”. Statistics, Optimization & Information Computing 14, no. 6 (November 10, 2025): 3589–3632. Accessed May 7, 2026. https://iapress.org/index.php/soic/article/view/3022.