References for: A chronology of pi

D H Bailey, J M Borwein, P B Borwein, and S Plouffle, The quest for Pi, The Mathematical Intelligencer 19 (1997), 50-57.
JOC/EFR September 2000

MacTutor History of Mathematics
[http://www-history.mcs.st-andrews.ac.uk/HistTopics/References/Pi_chronology.html]