 | Up a level |
Ridgway, Paul F; Guller, Ulrich (2009). Interpreting study designs in surgical research: a practical guide for surgeons and surgical residents. Journal of the American College of Surgeons, 208(4), pp. 635-45. New York, N.Y.: Elsevier 10.1016/j.jamcollsurg.2009.01.005
