https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-43
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-40
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-42
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-41
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-39