Remeslennikov , V. N. “Ǝ-Free Groups As Groups With the Length Function”. Ukrains’kyi Matematychnyi Zhurnal 44, no. 6 (July 7, 1992): 813–818. Accessed December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/8014.