About some comparison theorems for two-dimentional linear systems of differential equations and their applications

Assuming continuity, monotony and sign-constancy of coefficients of the second order linear: on a finite interval, are proved comparison theorems, which allow to reduce the determination of zeros of the components of the solutions of some systems for the definition of the number roots of the definite equation. There are also sufficient criteria for the oscillation and nonoscillation system in the work.