V. S. Il'kiv and B. I. Ptashnik, “Representation and investigation of solutions of a nonlocal boundary-value problem for a system of partial differential equations”, Ukr. Mat. Zhurn., vol. 48, no. 2, pp. 184–194, Feb. 1996, Accessed: Apr. 09, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5346