1. Fixed point theorems for operators with PPF dependence in Banach spaces;Bernfeld;Appl. Anal.,1977
2. V. Lakshmikantham, Periodic boundary value problems for first and second-order differential equations, to appear.
3. V. Lakshmikantham, G. S. Ladde, and A. S. Vatsala, “Monotone Iterative Techniques for Nonlinear Differential Equations,” Pitman, London, in press.