Anop, A. V., T. M. Kasirenko, and A. A. Murach. “Irregular Elliptic Boundary-Value Problems and Hörmander Spaces”. Ukrains’kyi Matematychnyi Zhurnal 70, no. 3 (March 25, 2018): 299–317. Accessed December 5, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/1558.