. 2014 Nov 5;30(9):1152–1161. doi: 10.1093/heapol/czu120
Published by Oxford University Press in association with The London School of Hygiene and Tropical Medicine © The Author 2014.
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work properly cited. For commercial re-use, please contact journals.permissions@oup.com