A. A. Berezovsky, I. M. Konet, M. P. Lenyuk, A. M. Samoilenko, and Y. V. Teplinsky, “Ukrainian school-seminar ‘Nonlinear boundary value problems of mathematical physics and applications’”, Ukr. Mat. Zhurn., vol. 49, no. 4, pp. 613–617, Apr. 1997, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5041