GENCHEV, T. Opening address to the Session (in Bulgarian). Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 89, p. 9–10, 1997. Disponível em: https://stipendii.uni-sofia.bg/index.php/fmi/article/view/349. Acesso em: 21 nov. 2024.