On the application of one M.G.Krein's result to the spectral analysis of   Sturm-Liouville operators
  Discovered by M.G.Krein analogy between polinomials orthogonal on the unit circle and generalized eigenfunctions of certain differential systems is used to obtain some new results in the spectral analysis of Sturm-Liouville operators. Some properties of Dirac-type differential systems are studied. 
S. A. Denisov (Moscow State University)