https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-7-52
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-7-54
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-7-53