"Written by two distinguished specialists in both research and
education, the book represents an excellent introduction to a subject of
increasing power and importance in today's mathematics. It is designed
for senior undergraduate and graduate students in mathematics,
engineering, etc., but it should be welcome in the library of any person
interested in operator theory and its applications." - F.-H. Vasilescu
for AMS "The text is self-contained as it is possible, and contains a
large number of exercises. It is highly offered to graduate and senior
undergraduate students in mathematics." -- L. Gehér for Acta Sci. Math.
(Szeged)