This paper extends the idea of Lindstedt s frequencies expansion into the non-linear autonomous sys-tems with many degrees of freedom and describes a multiple-frequency perturbation approach of the phase-locked periodic solutions for the case of the internal resonance by way of the non-linear trasformation ofthe independent variable.

The defining of thawing cycle of natural thawing method in the slicing of placer gold deposit in permafrost horizon;

Existence of periodic solutions to ecological model of microbes;

Exponential stability and existence of periodic solutions for a class of recurrent neural networks with delays;

On the existence theorem of periodic solution for differential inclusion;

Existence of periodic solutions for a class of non-autonomous second order Hamiltonian Systems;

Existence theorem of periodic solutions for a class of ordinary differential systems;

Existence of periodic solutions for p-Laplacian differential equation with Nagumo condition;

Uniqueness of almost periodic solution of an epidemic SIS model with variable coefficient;

Global asymptotic stability of almost periodic solutions for a predator-prey system;

Existence and uniqueness of almost periodic solutions to the retarded Liénard equation;