https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-4-19
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-4-20
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-4-18