doi:10.1093/ije/dys020
Int J Epidemiol 2012;41:210–17
This article was published with the incorrect copyright information; the licence line should have appeared as below:
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc/3.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com.