V. A. Gor'kavyi and E. N. Nevmerzhitskaya, “Two-dimensional pseudospherical surfaces with degenerate Bianchi transformation”, Ukr. Mat. Zhurn., vol. 63, no. 11, pp. 1460–1468, Nov. 2011, Accessed: Feb. 16, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2818