ČUPONA, Ǵorǵi; CELAKOSKI, Naum; ILIĆ, Snežana. GROUPOID POWERS. Matematichki Bilten, [S. l.], v. 25, n. 1, p. 5–12, 2001. Disponível em: https://bilten.smm.org.mk/index.php/bilten/article/view/1659. Acesso em: 14 aug. 2026.