ABSTRACT
In this chapter we state some definitions and some known results that will be useful in the subsequent chapters. For details, see [12], [13], [84], [95], [96], [130], [131], [147], [202], [211], and [213]. The results from Theorem 1.6.7 to the end of this chapter were recently
obtained by the authors while working on various special cases of rational difference equations and provide useful generalizations and some unifications in some special cases.
