Oscillation Properties of some Differential Equations

In recent years there has been much research activity concerning the oscillation of solutions of delay differential equations. To a large extent, this is due to the realization that delay differential equations are important in applications. New applications which involve delay differential equations continue to arise with increasing frequency in the modelling of diverse phenomena in physics, biology, ecology, and physiology. So, ¿nding the solutions of the differential equations or deducing important characteristics of them has received the attention of many authors. Actually, we have greatly less results for third and fourth order differential equations than for the ¿rst or second order equations. So, the main objective of this Book is to shed light on many equations of third and fourth order, through studying the asymptotic behavior of solutions of those equations by different methods and comparison of results. Our results in this Book not only generalize some of the previous results, but also improve the earlier ones (as described in the examples and remarks through chapters). Also, another main objective of this Book is to contribute to the great development of the oscillation