Infant Circumcision With Anesthesia: Does it Really Help the Pain?
http://www.thewholenetwork.org/14/post/2011/08/infant-circumcision-with-anesthesia-does-it-really-help-the-pain.html

Research Study: 11 Boys: Circumcised with anesthetic. 13 Boys: Circumcised without an anesthetic. When adrenal cortisol levels were compared, the anesthetic did not reduce the amount. Circumcision hurts, and it STILL hurts even if with anesthetic. 
http://cpj.sagepub.com/cgi/content/abstract/25/8/412 

Study shows that infants feel and remember circumcision pain 
http://www.sickkids.ca/aboutsickkids/newsroom/past-news/1997/study-shows-that-infants-feel-and-remember-circumcision-pain.html 

Here is a concise, easy to read excerpt from Dr. David B. Chamberlain. His paper includes 136 APA-quality citations on the history of our concept of pain in babies: 
http://www.drmomma.org/2010/01/babies-do-feel-pain.html 

Here is a study that found when babies experienced pain it reduced opioid receptors in their brains which decreased pain sensitivity in adulthood: 
http://www.sciencedaily.com/releases/2009/09/090927130048.htm 

Pain of Circumcision and Pain Control
http://www.cirp.org/library/pain/  

Pain Response During Circumcision
http://www.circumcision.org/response.htm  

Pain and Pain Management in Newborn Infants: A Survey of Physicians and Nurses
http://pediatrics.aappublications.org/cgi/content/full/100/4/626  

Percentage of Pain Control Actually Used 
http://pediatrics.aappublications.org/cgi/content/full/101/3/423  

“Up to 96 percent of the babies in the United States and Canada receive no anesthesia when they are circumcised, according to a report from the University of Alberta in Edmonton. “ 
http://www.cnn.com/HEALTH/9712/23/circumcision.anesthetic/