- Correspondence to Dr Soumaya Ben Khedher, CESP Centre for Research in Epidemiology and Population Health 16 avenue Paul Vaillant Couturier, 94807 Villejuif Cedex, France;
- Received 28 September 2016
- Revised 6 April 2017
- Accepted 13 April 2017
- Published online 10 May 2017.
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