The last fifty years have witnessed several monographs and hundreds of
research articles on the theory, constructive methods and wide spectrum
of applications of boundary value problems for ordinary differential
equations. In this vast field of research, the conjugate (Hermite) and
the right focal point (Abei) types of problems have received the maximum
attention. This is largely due to the fact that these types of problems
are basic, in the sense that the methods employed in their study are
easily extendable to other types of prob- lems. Moreover, the conjugate
and the right focal point types of boundary value problems occur
frequently in real world problems. In the monograph Boundary Value
Problems for Higher Order Differential Equations published in 1986, we
addressed the theory of conjugate boundary value problems. At that time
the results on right focal point problems were scarce; however, in the
last ten years extensive research has been done. In Chapter 1 of the
mono- graph we offer up-to-date information of this newly developed
theory of right focal point boundary value problems. Until twenty years
ago Difference Equations were considered as the dis- cretizations of the
differential equations. Further, it was tacitly taken for granted that
the theories of difference and differential equations are parallel.
However, striking diversities and wide applications reported in the last
two decades have made difference equations one of the major areas of
research.