stochastic Markov systems, averaging, Functional limit theorems; invariance principles, Perturbation theory of linear operators, One-parameter semigroups and linear evolution equations, Ordinary differential equations and systems with randomness, stochastic systems, diffusion approximation, singularly perturbed stochastic systems, Nonlinear differential equations in abstract spaces, ????????????, Stochastic integral equations, Singular perturbations for ordinary differential equations, diffusion approximation schemes, Continuous-time Markov processes on general state spaces, phase merging, singular perturbations, Markov switchings, random evolutions, Ergodic theory of linear operators, Generation, random and stochastic difference and differential equations, reducible invertible operators, Singular perturbations of ordinary differential equations