"The author is an important contributor to the subject, and the volume contains many of his results. The book is carefully written … Over 250 exercises, an up-to-date bibliography and an extensive index add to the value of the book. This volume is especially recommended to students and researchers in Algebraic Number Theory, but any algebraist will find here interesting ideas and information."- Studia Universitatis Babes-Bolyai Series Mathematica, Vol. XLVIII, No. 4, 2003"The book is rich in many examples and exercises."-Zentralblatt MATHPromo Copy