1. Hills Equation;Magnus,1966
2. Ordinary Differential Equations;Hale,1969
3. Positive periodic solutions of Hill’s equations with singular nonlinear perturbations;Chu;Nonlinear Anal.,2008
4. A non-homogeneous Hill’s equation;Shadman;Appl. Math. Comput.,2005
5. Reflecting Function and Discussion of Many-Dimensional Differential system;Mironenko,2004