1. N. E. Tovmasyan, Non-Regular Differential Equations and Calculation of Electromagnetic Fields (World Scientific, Singapore, 1998). https://doi.org/10.1142/9789812816627
2. J.-L. Lions and E. Magenes, Problemes aux Limites non Homogenes a Donnees Irregulieres (Dunod, Paris, 1968).
3. A. O. Babayan, ‘‘The unique solvability of a Dirichlet problem for fourth order elliptic equations,’’ J. Contemp. Math. Anal. 34 (5), 1–15 (1999).
4. A. O. Babayan, ‘‘Dirichlet problem for a properly elliptic equation in a unit disk,’’ J. Contemp. Math. Anal. 38 (6), 19–28 (2003).
5. S. Axler, P. Bourdon, and W. Ramey, Harmonic Function Theory, Graduate Texts in Mathematics, Vol. 137 (Springer, New York, 2001). https://doi.org/10.1007/978-1-4757-8137-3