“On the theorems of Borsuk-Ulman and Ljusternik-Shnirelman-Borsuk” (1993) Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, 84, pp. 83–89. Available at: https://annual.uni-sofia.bg/index.php/fmi/article/view/471 (Accessed: 11 January 2026).