Kurdachenko, L. A., L. A. Kurdachenko, J. Otal, and A. A. Pypka. “On Some Properties of the Central and Generalized Central Series of Groups”. Reports of the National Academy of Sciences of Ukraine, no. 1 (January 8, 2025): 20–24. Accessed May 12, 2025. https://nasu-periodicals.org.ua/index.php/dp/article/view/12950.