Ustyanich, E.P., and A.E. Ustyanich. “About a Practical Method of Determining the Length of an Ellipse”. Reports of the National Academy of Sciences of Ukraine, no. 9 (September 28, 2020): 10–18. Accessed June 19, 2026. https://nasu-periodicals.org.ua/index.php/dp/article/view/2020-9-2.