Drach, K.D. “About the Isoperimetric Property of λ-Convex Lunes on the Lobachevsky Plane”. Reports of the National Academy of Sciences of Ukraine, no. 11 (March 11, 2025): 11–15. Accessed May 10, 2026. https://nasu-periodicals.org.ua/index.php/dp/article/view/16813.