(1) http://www.psychiatry.org/addiction
(2) http://www.samhsa.gov/data/NSDUH/2k11Results/NSDUHresults2011.htm
(3) http://www.drugabuse.gov/publications/topics-in-brief/drugs-brains-behavior-science-addiction
(4) http://www.drugabuse.gov/publications/addiction-science-molecules-to-managed-care/introduction/drug-abuse-costs-united-states-economy-hundreds-billions-dollars-in-increased-health