Kharibegashvili, S., and B. Midodashvili. “On the Solvability of a Problem Nonlocal in Time for a Semilinear Multidimensional Wave Equation”. Ukrains’kyi Matematychnyi Zhurnal 67, no. 1 (January 25, 2015): 88–105. Accessed April 25, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1965.