ЧУПОНА, Ѓ. 3A n-АРНИТЕ ПОТПОЛУГРУПИ. Matematichki Bilten, [S. l.], v. 11, n. 1, 1961. Disponível em: https://bilten.smm.org.mk/index.php/bilten/article/view/1258. Acesso em: 13 jun. 2026.