References
- Bainov , D.D. , Simeonov , P.S. and Lakshmikantham , V. “ Theorv of Impulsive Differential Eauations ” .
- Ladde , G. S. , Lakshmikatham , V. and Vatsala , A. S. 1985 . “ Monotone Iterative Technique for Nonlinear Differential Equations ” . Boston : Pitman Advanced Publishing Program .