Petrov Ф.; Ninova Ю. In memoriam of Prof. Ivan Gantchev Donev. Mathematics and Education in Mathematics, [S. l.], v. 52, p. 101–133, 2023. DOI: 10.55630/mem.2023.52.101-133. Disponível em: https://smb.math.bas.bg/mem/index.php/memjournal/article/view/77. Acesso em: 6 oct. 2026.