Shtelik V. G.
Ukr. Mat. Zh. - 1962. - 14, № 4. - pp. 372-382
The authors consider the equation of a nonlinear non-autonomous mathematical pendulum in various approximations from the viewpoint of oscillation, increase and damping of the amplitude and stability of the position of equilibrium; a classification of the motions is presented.
On the sufficient conditions of stability of the solutions of some nonlinear equations of the second order
Ukr. Mat. Zh. - 1962. - 14, № 1. - pp. 109-113