A respectable period of time has passed since the first edition of this book, during which several pressures have necessitated a second edition. Most important, there were the inadvertent errors needing correction. The field has also had some significant changes, not so much in methodology perhaps as in context, regulation, and the like. I can say some things more clearly now than previously because many issues are better defined or I care more (or less) about how the discussion will be received.