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2. The monotone method for first order problems with linear and nonlinear boundary conditions;Cabada;Appl. Math Comput.,1994
3. Impulsive differential equations of first order with periodic boundary conditions;Pierson Gorez;Diff. Eqns Dyn. Sys.,1993
4. Monotone Iterative Techniques for Nonlinear Differential Equations;Ladde,1985
5. Theory of Impulsive Differential Equations;Lakshmikantham,1989