Langley John D, Kypri Kypros, Stephenson Shaun C R
Injury Prevention Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin 9000, New Zealand.
BMJ. 2003 Nov 1;327(7422):1023-4. doi: 10.1136/bmj.327.7422.1023.