https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-6-15
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-6-17
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-6-16
https://ij-healthgeographics.biomedcentral.com/articles/10.1186/1476-072X-6-18