In Memoriam Iordan Iordanov (1948-2021). Annual of Sofia University St. Kliment Ohridski. Faculty of Mathematics and Informatics, [S. l.], v. 111, p. 5–24, 2024. DOI: 10.60063/gsu.fmi.111.5-24. Disponível em: https://annual.uni-sofia.bg/index.php/fmi/article/view/995. Acesso em: 14 dec. 2025.