http://www.veganforum.com/forums/showthread.php?196-50-ways-to-develop-B12-deficiency
http://www.aafp.org/afp/2003/0301/p979.html
http://www.veganhealth.org/b12/sympt
http://b12awareness.org/tag/weston-a-price-foundation/
http://brainblogger.com/2014/07/30/vitamin-b12-deficiency-and-its-neurological-consequences/
http://neurotalk.psychcentral.com/post698522-70.html