2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/129028We review the papers [1-3]. We discuss possibilities of studying the quasi-normal modes of black holes that are not known in an analytical form. Such black holes appear as solutions in various theoretical models and real astrophysical approximations when one takes into account the black hole neighborhood.3 pages, 1 figure, RevTeX. Talk to be given at the seminar of Russian Gravitational SocietyGeneral Relativity and Quantum Cosmologytext