Bondar’O. P. “Generalized (CO)Homology Length of a Manifold and Functions With Singular Submanifolds”. Ukrains’kyi Matematychnyi Zhurnal 48, no. 6 (June 25, 1996): 843-846. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5284.