https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-10-40
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-10-41
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-10-42