The supplemental, optional reading [1] gives additional background on the overall topic of Chapter 15, that is, extended Boolean approaches. It focuses on the P-norm model, and gives experimental evidence for its utility. Less relevant to the course focus, but also of interest, is the discussion of the mathematical properties of the P-norm model, which some feel do not adequately deal with the requirements of purist Boolean searchers.
In the rest of this collection of readings there are many typographical and other minor errors. Most are detailed below - if any others are found, please tell the instructor so a complete list can be developed. In addition, many comments, clarifications, points of disagreement, etc. are provided. Note: these refer to the first printing of the text, and should have been corrected in your edition.