https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-9-59
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-9-58
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-9-57