Sackett, D.L., Rosenberg, W.A., Gray, J.A., Haynes, R.B. & Richardson, W.S., 1996. Evidence based medicine: what it is and what it isn't. BMJ, 312(7023): 71–72. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2349778/. The foundational article in evidence-based medicine, of which critical appraisal forms a part.