KOSTRA, Juraj. Open problems on the relation between additive and multiplicative structure. Annales Mathematicae Silesianae, [S. l.], v. 16, p. 21–25, 2003. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/14105. Acesso em: 5 dec. 2025.