ChepurukhinaI. S., and MurachA. A. “Elliptic Boundary-Value Problems in the Sense of Lawruk on Sobolev and Hörmander Spaces”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 67, no. 5, May 2015, pp. 672–691, https://umj.imath.kiev.ua/index.php/umj/article/view/2014.