1. From Sólmundur Jónsson, 15 July, 2003, on HD's "How to Handle Missing Information without Using Nulls"

2. Not a question, but a critique from Maurice Gittens, and Hugh Darwen's response.

3. From Mark Friedenbach, 30 May, 2005, on inheritance of update opera

4. An interview with Chris Date and Hugh Darwen, "No! to SQL! No! to NoSQL!", in the August 2013 issue of NoCOUG Journal