1. Asymptotic Methods in the Theory of Non-linear Oscillations;Bogoliubov,1974
2. Mathematical Methods of Classical Mechanics;Arnol'd,1974
3. Two-frequency Fermi mapping;Howard;Physica D. Non-linear phenomena,1982
4. Small denominators and the problem of stability in classical and celestial mechanics;Arnol'd;Uspekhi Matem. Nauk.,1963
5. Exponential estimate of the time of stability of Hamiltonian systems close to integrable;Nekhoroshev,1979