1. N. Krylov and N. Bogoliubov,Introduction to Nonlinear Mechanics, translated by S. Lefshetz (Princeton University Press, Princeton, New Jersey, 1947).
2. N. Bogoliubov and Y. A. Mitropolskii,Asymptotic Methods in the Theory of Nonlinear Oscillations(Gordon and Breach Science Publishers, New York, 1961) [translated from the Russian].
3. CIX. A Technique for rendering approximate solutions to physical problems uniformly valid
4. On a New Method in the Theory of Irreversible Processes
5. The foundations of nonequilibrium statistical mechanics, I