- Correspondence to Dr B Barr, Department of Public Health and Policy, Institute of Psychology, Health and Society, University of Liverpool, Whelan Building, Liverpool L69 3GB, UK;
- Received 16 June 2015
- Revised 28 August 2015
- Accepted 5 October 2015
- Published in print 1 April 2016.
- Published online 9 March 2016.
- Published first 16 November 2015.
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