Stegantseva, P. G., and A. V. Skryabina. “Topologies on the $n$-Element Set That Consistent With Close to the Discrete Topologies on $(n −1)$-Element Set”. Ukrains’kyi Matematychnyi Zhurnal 73, no. 2 (February 22, 2021): 238 - 248. Accessed March 29, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/6174.