- Correspondence to:
Professor R F Logan
Division of Epidemiology and Public Health, School of Community Health Sciences, University of Nottingham Medical School, Nottingham NG7 2UH, UK;
- Accepted June 17, 2005
- Revised June 14, 2005
- First published June 30, 2005.
Conflict of interest: Dr Van-Staa is an employee at Proctor and Gamble, and Dr Card and Professor Logan have both received hospitality from Proctor and Gamble.
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