https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-47
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-46
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-45
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-49
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-44
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-48