et. al., V. Sudha. “Characterizations of Nnce-Open and Nnce-Closed Functions”. Turkish Journal of Computer and Mathematics Education (TURCOMAT) 12, no. 1S (April 11, 2021): 351–356. Accessed May 2, 2024. https://turcomat.org/index.php/turkbilmat/article/view/1849.