Shalini, A.Francina. “ÄŒech Ï€gβ - CLOSED SETS IN CLOSURE SPACES”. Journal of Global Research in Mathematical Archives(JGRMA) 1, no. 4 (May 11, 2013): 50–56. Accessed May 9, 2025. https://www.jgrma.com/index.php/jgrma/article/view/54.