MikhailetsV. A., and MurachA. A. “Improved Scales of Spaces and Elliptic Boundary-Value Problems. II”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, no. 3, Mar. 2006, pp. 352–370, https://umj.imath.kiev.ua/index.php/umj/article/view/3459.