TCHUDAKOFF, N. G. Theory of the Characters of Number Semigroups. The Journal of the Indian Mathematical Society, [S. l.], v. 20, n. 1-3, p. 11–15, 1956. DOI: 10.18311/jims/1956/16982. Disponível em: https://www.informaticsjournals.com/index.php/jims/article/view/16982. Acesso em: 3 may. 2024.