https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-11-16
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-11-15
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-11-17