Dubatovskaya, M.V., and S.V. Rogosin. “On an Exact Description of the Schottky Groups of Symmetries”. Mathematical Modelling and Analysis 9, no. 2 (June 30, 2004): 137-148. Accessed December 2, 2024. https://mma.vgtu.lt/index.php/MMA/article/view/9723.