- Correspondence to Nadine S M Offermans, Department of Epidemiology, Maastricht University Medical Centre, P.O. Box 616, 6200 MD Maastricht, The Netherlands;
- Accepted May 8, 2012
- First published June 12, 2012.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.