CHINESE JOURNAL OF EPIDEMIOLOGY, Volume 19, Issue 5,1998, , doi:10.3760/j.issn:0254-6450.1998.05.029
CHINESE JOURNAL OF EPIDEMIOLOGY, Volume 19, Issue 5,1998, , doi:10.3760/j.issn:0254-6450.1998.05.031
CHINESE JOURNAL OF EPIDEMIOLOGY, Volume 19, Issue 5,1998, , doi:10.3760/j.issn:0254-6450.1998.05.019
CHINESE JOURNAL OF EPIDEMIOLOGY, Volume 19, Issue 5,1998, , doi:10.3760/j.issn:0254-6450.1998.05.006
CHINESE JOURNAL OF EPIDEMIOLOGY, Volume 19, Issue 5,1998, , doi:10.3760/j.issn:0254-6450.1998.05.018