SENASHOV, V.I.; PARASCHUK, I.A. On a bottom layer in a group. Bulletin of the Karaganda University. Mathematics Series, [S. l.], v. 100, n. 4, p. 136–142, 2020. DOI: 10.31489/2020m4/136-142. Disponível em: http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/394. Acesso em: 4 sep. 2025.