1. Russo MW, Wei JT, Thiny MT, Gangarosa LM, Brown A, Ringel Y, et al. Digestive and liver diseases statistics, 2004. Gastroenterology. 2004 May;126(5):1448–53.
2. Legorreta AP, Silber JH, Costantino GN, Kobylinski RW, Zatz SL. Increased cholecystectomy rate after the introduction of laparoscopic cholecystectomy. JAMA. 1993 Sep 22–29;270(12):1429–32.
3. McPherson K, Wennberg JE, Hovind OB, Clifford P. Small-area variations in the use of common surgical procedures: an international comparison of New England, England, and Norway. N Engl J Med. 1982 Nov 18;307(21):1310–4.
4. Laycock WS, Siewers AE, Birkmeyer CM, Wennberg DE, Birkmeyer JD. Variation in the use of laparoscopic cholecystectomy for elderly patients with acute cholecystitis. Arch Surg. 2000 Apr;135(4):457–62.
5. Weeks WB, Paraponaris A, Ventelou B. Geographic variation in rates of common surgical procedures in France in 2008–2010, and comparison to the US and Britain. Health Policy. 2014 Nov;118(2):215–21.