Трпеновски, Б. Л. “ЗА N-ГРУПОИДИТЕ СО ЦЕНТРАЛНИ НЕУТРАЛНИ ЕЛЕМЕНТИ”. Matematichki Bilten 13, no. 1 (January 1, 1963). Accessed June 13, 2026. https://bilten.smm.org.mk/index.php/bilten/article/view/1272.