FedchenkoYu. S. “Normal and Tangential Geodesic Deformations of the Surfaces of Revolution”. Ukrains’kyi Matematychnyi Zhurnal 61, no. 10 (October 25, 2009): 1396-1402. Accessed November 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3109.