--through Mrs. D and Rose, who post at various boards.

Rose is in the process of building a massive B12 website, with exhaustive citations. It's a work in progress, but can be reached at:

http://roseannster.googlepages.com/home

There are also a lot of links through the Vitamins/Mineral/Supplements forum here:

http://neurotalk.psychcentral.com/forumdisplay.php?f=49