1. H.D. Alber, A quasi-periodic boundary value problem for Laplacian and continuation of its resolvent, Proc. Roy. Soc. Edinburgh. Sect. A. Math 82 (1979), 251–272.
2. V.M. Babich, On the existence theorem of solutions of the Dirichlet and the Neiman problems for the Helmholtz equation in the quasi-periodical case, Siberian Math. Jour 39 (1988), no. 2, 3–9.
3. V.F. Badyukov, The uniqueness theorem for the scattering problem by a periodical grating, Vestnik Leningrad Univ 19 (1977), 88–92 (Russian).
4. V.F. Badyukov, The existence theorem for the scattering problem by a periodical grating, Vestnik Leningrad Univ 20 (1978), 81–88 (Russian).
5. A.G. Belyaev, A.S. Mikheev and A.S. Shamaev, The scattering of a plane wave by a rapidly oscillating grating, Journal of Numer. Math. and Math. Physics 32 (1992), no. 3, 1253–1272 (Russian).