1. World Bank. Total health expenditures as percentage of GDP. Updated 2013. Available at: http://data.worldbank.org/indicator/sh.xpd.totl.zs. Accessed April 18, 2014.
2. The Commonwealth Fund. Explaining high health care spending in the United States: an international comparison of supply, utilization, prices, and quality. Available at: http://www.commonwealthfund.org/publications/issue-briefs/2012/may/high-health-care-spending.aspx. Accessed April 18, 2014.
3. Volume standards for high-risk surgical procedures: potential benefits of the Leapfrog initiative;Birkmeyer;Surgery,2001
4. US Department of Veterans Affairs. VA medical centers designated for surgical complexity. Available at: http://www.patientcare.va.gov/20100518a1.asp. Accessed April 18, 2014.
5. Weiss AJ, Elixhauser A, Andrews RM. Statistical brief #170: characteristics of operating room procedures in U.S. hospitals, 2011. Available at: http://www.hcup-us.ahrq.gov/reports/statbriefs/sb170-operating-room-procedures-united-states-2011.jsp. Accessed April 18, 2014.