1. Bogolubov, N.N., Mitropolsky, Y.A.: Asymptotic Methods in the Theory of Nonlinear Oscillations. Gordon and Breach Science Publishers, New York (1961)
2. Volosov, V.M., Morgunov, B.I.: The Averaging Method in the Theory of Non-linear Oscillatory Systems. Moscow State Univ., Moscow (1971) in Russian
3. Mitropolsky, Yu.A.: The Method of Averaging in Nonlinear Mechanics. Naukova Dumka, Kiev (1971) in Russian
4. Demin, V.G., Konkina, L.I.: New Methods in Dynamics of a Rigid Body. Ilim, Frunze (1989) in Russian
5. Bulgakov, B.V.: Applied Theory of Gyroscopes, 3rd edn. Moscow State Univ., Moscow (1976) in Russian