1. D. Colton and R. Kress, Integral Equation Methods in Scattering Theory (Wiley, New York, 1984; Mir, Moscow, 1987).
2. W. McLean, Strongly Elliptic Systems and Boundary Integral Equations (Cambridge Univ. Press, Cambridge, 2000).
3. A. N. Tikhonov and A. A. Samarskii, Equations of Mathematical Physics (Nauka, Moscow, 1999; Dover, New York, 2011).
4. A. A. Samarskii, The Theory of Difference Schemes (Nauka, Moscow, 1977; Marcel Dekker, New York, 2001).
5. F. Ihlenburg, Finite Element Analysis of Acoustic Scattering (Springer-Verlag, New-York, 1998).