https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-9-41
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-9-43
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-9-42