CHINESE JOURNAL OF OBSTETRICS AND GYNECOLOGY, Volume 44, Issue 11,2009, Pages 861-864, doi:10.3760/cma.j.issn.0529-567x.2009.11.015
CHINESE JOURNAL OF OBSTETRICS AND GYNECOLOGY, Volume 44, Issue 11,2009, Pages 876-878, doi:10.3760/cma.j.issn.0529-567x.2009.11.020