Berezovsky, A. A., M. P. Lenyuk, and A. M. Samoilenko. “School-Seminar ‘Nonlinear Boundary-Value Problems in Mathematical Physics and Their applications’”. Ukrains’kyi Matematychnyi Zhurnal 48, no. 6 (June 25, 1996): 863–865. Accessed December 5, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5289.