1. F. Fleury, E. Sánchez-Palencia, “Asymptotic and spectral properties of the acoustic vibrations of body perforated by narrow channels,” Bull. Sci. Math. II Sér., 110, 149–176 (1986).
2. E. Ya. Khruslov, “On resonance phenomena in a diffraction problem” [in Russian], Teor. Funkts., Funkts. Anal. Pril. 10, 113–120 (1968).
3. V. P. Kotlyarov and E. Ya. Khruslov, “On limit boundary condition in a Neumann problem” [in Russian], Teor. Funkts., Funkts. Anal. Pril. 10, 83–96 (1970).
4. V. A. Marchenko and E. Ya. Khruslov, Boundary Value Problems in Domains with a Fine-Grained Boundary [in Russian], Naukova Dumka, Kiev (1974).
5. T. A. Mel’nik, S. A. Nazarov, “The asymptotic structure of the spectrum in the problem of harmonic oscillations of a hub with heavy spokes” [in Russian], Dokl. Akad. Nauk, Ross. 102 Akad. Nauk 333, No. 1, 13–15 (1993);