Chinese Journal of Obstetrics and Gynecology, Volume 54, Issue 7,2019, Pages 451,
Chinese Journal of Obstetrics and Gynecology, Volume 54, Issue 7,2019, Pages 452-457, doi:10.3760/cma.j.issn.0529-567x.2019.07.004
Chinese Journal of Obstetrics and Gynecology, Volume 54, Issue 7,2019, Pages 451,