ABSTRACT
There are so many applications of pseudodifferential operators that it seems impossible to describe them completely. Books have been written on this subject (cf. [8,9,11,13]) but none claims to give a general description of all possible applications. Moreover, this introductory course was not intended to develop applications but only to describe the very basic elements of the theory itself. However, it would have been very artificial to drop the applications completely, since the main motivations of a theory lie in its ability to solve problems.
