1. Theory of Impulsive Differential Equations;Lakshmikantham,1989
2. Upper and lower solutions in the theory of ODE boundary value problems: classical and recent results;De Coster,1996
3. An overview of the method of lower and upper solutions for ODEs;De Coster,2001
4. The lower and upper solutions method for boundary value problems;De Coster,2004
5. Two-Point Boundary Value Problems: Lower and Upper Solutions;De Coster,2006