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 December 5, 2025. http://www.iapress.org/index.php/soic/article/view/3022.