Nikola Obreshkoff (1896-1963). Encomium. Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 89, p. 11–17, 1997. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/350. Acesso em: 14 dec. 2025.