ABSTRACT
CHAPTER 4
4.1. Introduction
The study of oscillation for second order ordinary differential equations is interesting from the theoretical as well as the practical point of view. There are many articles and books studying this topic. The survey paper by Wong [267] contains a complete bibliography up to 1968. Also, for a detailed account on second order nonlinear differential equations, see the paper by Kartsatos [142], which gives more than 300 references. In this chapter, we will present some criteria for oscillation and for the existence of positive solutions of nonlinear differential equations of second order, mainly including some contributions of the authors and their colleagues.
