Romanovskii R. K., Mendziv M. V.
          Stability of solutions to the Cauchy problem for a plane hyperbolic system with   time-periodic coefficients
        Considering a plane hyperbolic system with time-periodic coefficients,  we construct a version of the direct Lyapunov method with the condition on the  derivative of the Lyapunov functional along the trajectories of the system  which is weakened by use of periodicity of the coefficients. We exhibit an  illustrative example.