The items listed below, all of them just a very few pages, are notes that I have written in past terms in answer to student questions that required longer answers. None of them are essential to the course, but you are welcome - in fact, encouraged - to browse through them and read anything that you find interesting. If any of the issues that stimulated the writing of any of these notes pops up in our class, I'll post a response referencing the appropriate note - and if really significant, post a class announcement.