1. Elfimov, V.S.: Existence of periodic solutions of equations of motion of a solid body similar to the Lagrange gyroscope. PMM 42(2), 251–258 (1978)
2. Malkin, I.G.: Some problems in the theory of nonlinear oscillations. United States Atomic Energy Commission, Technical Information Service, ABC. Tr-3766 (1959)
3. Nayfeh, A.H.: Perturbations Methods. Wiley-Interscience, New York (1973)
4. Arkhangel’skii, Iu.A.: Periodic solutions of quasilinear autonomous system which have first integrals. PMM 27(2), 369–372 (1963)
5. El-Barki, F.A., Ismail, A.I.: Limiting case for the motion of a rigid body about a fixed point in the Newtonian force field. ZAMM 75(11), 821–829 (1995)