MARKOVSKI, Smile. FREE \((V;n,m)\)-GROUPOIDS. Matematichki Bilten, [S. l.], v. 16, n. 1, p. 5–16, 1992. Disponível em: https://bilten.smm.org.mk/index.php/bilten/article/view/1509. Acesso em: 14 aug. 2026.