Khachatryan Р. А. . “Gradient Projection Method and Continuous Selections of Multivalued Mappings”. Bulletin of L.N. Gumilyov Eurasian National University. Mathematics, Computer Science, Mechanics Series, vol. 124, no. 3, Sept. 2018, pp. 95-100, https://bulmathmc.enu.kz/index.php/main/article/view/27.