ZelinskiiYu. B., KlishchukB. A., and TkachukM. V. “Theorems on Inclusion for Multivalued Mappings”. Ukrains’kyi Matematychnyi Zhurnal 66, no. 7 (July 25, 2014): 1003–1005. Accessed November 21, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2194.