1. Impact of variability among surgeons on postoperative morbidity and mortality and ultimate survival;McArdle, C.S.; Hole, D.;BMJ,1991
2. Armitage P, Berry G. Statistic methods in medical research. Oxford: Blackwell Scientific, 1987:205.
3. Working for patients;Secretaries of State for Health, Wales, Northern Ireland, and Scotland,555.)
4. How much variation in referral rates among general practitioners is due to chance?;Moore, A.T.; Roland, M.O.;BMJ,1989
5. Surgeons who undertake surgery for colorectal cancer;Soutter, W.P.;BMJ,1991