https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-32
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-33
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-35
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-37
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-36
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-38
https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-4-34