Zelinka, B. “Strongly Connected Digraphs in Which Each Edge Is Contained in Exactly Two Cycles”. Acta Cybernetica 4, no. 2 (January 1, 1979): 203–205. Accessed January 26, 2026. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3178.