Anop, A. V., T. M. Kasirenko, and A. A. Murach. 2018. “Irregular Elliptic Boundary-Value Problems and Hörmander Spaces”. Ukrains’kyi Matematychnyi Zhurnal 70 (3), 299-317. https://umj.imath.kiev.ua/index.php/umj/article/view/1558.