1. 1. Lions, J.-L. & Magenes, E. (1972). Non-homogeneous boundary-value problems and applications, vol. I. Berlin: Springer.
2. 2. Lawruk, B. (1963). Parametric boundary-value problems for elliptic systems of linear differential equations. I. Construction of conjugate problems. Bull. Acad. Polon. Sci. Sér. Sci. Math. Astronom. Phys., 11, No. 5, pp. 257-267 (in Russian).
3. 3. Kozlov, V.A., Maz'ya, V.G. & Rossmann, J. (1997). Elliptic boundary value problems in domains with point singularities. Providence: Amer. Math. Soc.
4. 4. Roitberg, Ya.A. (1999). Elliptic boundary value problems in the spaces of distributions. Dordrecht: Kluwer.
5. Extended Sobolev scale and elliptic operators;Mikhailets;Ukr Math J 65 No 3,2013