ABSTRACT
Contemporary methods for solving inverse problems are gaining the increasing popularity. They are being used more and more in solving applied problems not only by professional mathematicians but also by investigators working in other branches of science. In order to make this book accessible not only to specialists but also to graduate and post-graduate students, we give a complete account of notions and definitions which will be used in the sequel. The concepts and theorems presented below are of an auxiliary nature and are included for references rather than for primary study. For this reason the majority of statements are quoted without proofs. We will also cite bibliographical sources for further, more detailed, information.
