N. A. . Davydov, “On properties of continuous mapings of nonlimited metric spaces”, Ukr. Mat. Zhurn., vol. 43, no. 3, pp. 422–427, Feb. 1991, Accessed: Jan. 12, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/9626