EndimioniG. “Hopficity and Co-Hopficity in Soluble Groups”. Ukrains’kyi Matematychnyi Zhurnal 56, no. 10 (October 25, 2004): 1335-1341. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3846.