Maslyuchenko VK, Fotii OH. Constancy of upper-continuous two-valued mappings into the Sorgenfrey line. Ukr. Mat. Zhurn. [Internet]. 2007Aug.25 [cited 2024Nov.24];59(8):1034–1039. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/3367