BOUMOVA, S.; DRENSKY, V. On cyclic invariants of the free associative algebra. Mathematics and Education in Mathematics, [S. l.], v. 55, p. 357–369, 2026. DOI: 10.55630/mem.2026.55.357-369. Disponível em: https://smb.math.bas.bg/mem/index.php/memjournal/article/view/258. Acesso em: 6 oct. 2026.