1. Sackett DL, Haynes RB, Guyatt GH, Tugwell P. Clinical Epidemiology: A Basic Science for Clinical Medicine, 2nd ed. Toronto: Little Brown and Company; 1991.
2. Joo HS, Wong J, Naik VN, Savoldelli GL. The value of screening preoperative chest x-rays: a systematic review. Can J Anesth 2005; 52:568–74.
3. Munro J, Booth A, Nicholl J. Routine preoperative testing: a systematic review of the evidence. Health Technol Assess 1997; 1:1–62.
4. Guidelines Advisory Committee. Clinical Practice Guidelines. Preoperative chest x-ray. http://gacguidelines. ca/article.pl?sid=02/11/15/1937251.
5. Davis DA, Taylor-Vaisey A. Translating guidelines into practice. A systematic review of theoretic concepts, practical experience and research evidence in the adoption of clinical practice guidelines. CMAJ 1997; 157:408–16.