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,
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