CHINESE JOURNAL OF OBSTEICS AND GYNECOLOGY, Volume 34, Issue 9,1999, Pages 573, doi:10.3760/j.issn:0529-567X.1999.09.032
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CHINESE JOURNAL OF OBSTEICS AND GYNECOLOGY, Volume 34, Issue 9,1999, Pages 569, doi:10.3760/j.issn:0529-567X.1999.09.022
CHINESE JOURNAL OF OBSTEICS AND GYNECOLOGY, Volume 34, Issue 9,1999, Pages 520, doi:10.3760/j.issn:0529-567X.1999.09.024