The major changes in this edition of the text are listed and explained in the Preface of the book. They include global improvements by updating and streamlining chapters as well as many local improvements aimed at simplification of the whole text. Speedy orientation is helped by chapter summaries at the end of the chapters, as in the last edition, and by subdividing sections into subsections with unnumbered headings. Resulting effects of these changes on the problem sets are as follows.