METEL'SKII , Yurii M. Regina Iosifovna Tyshkevich . Journal of the Belarusian State University. Mathematics and Informatics, [S. l.], n. 1, p. 84–85, 2020. Disponível em: https://journals.bsu.by/index.php/mathematics/article/view/1112. Acesso em: 17 jul. 2026.