[1]
H. J. Rivertz, “On an invariant on isometric immersions into spaces of constant sectional curvature”, Ukr. Mat. Zhurn., vol. 61, no. 12, pp. 1660–1704, Dec. 2009, Accessed: Feb. 13, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3129