Kasyanov, P. O., and V. S. Mel’nik. “On Properties of Subdifferential Mappings in Fréchet Spaces”. Ukrains’kyi Matematychnyi Zhurnal 57, no. 10 (October 25, 2005): 1385–1394. Accessed April 28, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3692.