- Correspondence to Dr Esther Crawley, Centre for Child and Adolescent Health, School of Social & Community Medicine, University of Bristol, Barley House, Oakfield Grove, Bristol BS8 2BN, UK;
- Received April 20, 2015
- Revised July 14, 2015
- Accepted August 4, 2015
- First published October 9, 2015.
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- Data supplement 1 - Online supplement
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