1. On Sturmian theory for second order systems;Ahmad,1983
2. Topologie;Alexandroff,1935
3. Oscillation Matrices and Kernels and Small Vibrations of Mechanical Systems;Gantmacher,1950
4. A nonselfadjoint dynamical system;Kreith,1974
5. Comparison and Oscillation Theory of Linear Differential Equations;Swanson,1968