VASSILEVA, A.; NIKOLOV, N. Fifty Spring Conferences of the Union of Bulgarian Mathematicians - the Tradition Continues. Mathematics and Education in Mathematics, [S. l.], v. 50, p. 9–22, 2021. Disponível em: https://smb.math.bas.bg/mem/index.php/memjournal/article/view/1. Acesso em: 7 oct. 2026.