1. An oscillation criterion for second order linear differential equations;Coles,1968
2. Kamenev type theorems for second order matrix differential systems;Erbe,1993
3. On nonoscillatory linear differential equations of second order;Hartman;Amer. J. Math.,1952
4. On self-adjoint differential equations of second order;Leighton;J. London Math. Soc.,1952
5. On a conjecture for oscillation of second order ordinary differential systems;Mingarelli,1981