- Correspondence to Professor G J Macfarlane, Epidemiology Group, University of Aberdeen, School of Medicine, Medical Sciences and Nutrition, Polwarth Building, Foresterhill, Aberdeen, Scotland AB25 2ZD, UK;
- Received 15 April 2016
- Revised 10 June 2016
- Accepted 14 June 2016
- Published online 4 July 2016.
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