T. M. Kasirenko and A. A. Murach, “Elliptic problems with boundary conditions of higher orders in Hörmander spaces”, Ukr. Mat. Zhurn., vol. 69, no. 11, pp. 1486–1504, Nov. 2017, Accessed: Jan. 27, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/1797