Operator theory in finite-dimensional vector spaces -- Perturbation theory in a finite-dimensional space -- to the theory of operators in Banach spaces -- Stability theorems -- Operators in Hilbert spaces -- Sesquilinear forms in Hilbert spaces and associated operators -- Analytic perturbation theory -- Asymptotic perturbation theory -- Perturbation theory for semigroups of operators -- Perturbation of continuous spectra and unitary equivalence