ZelinskiiY. B., KlishchukB. A., and TkachukM. V. “Theorems on Inclusion for Multivalued Mappings”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 66, no. 7, July 2014, pp. 1003–1005, https://umj.imath.kiev.ua/index.php/umj/article/view/2194.