Young S B, Rosenblatt P L, Pingeton D M, Howard A E, Baker S P
Department of Obstetrics and Gynecology, University of Massachusetts Medical Center, Worcester 01655, USA.
Am J Obstet Gynecol. 1995 Dec;173(6):1719-25; discussion 1725-6. doi: 10.1016/0002-9378(95)90416-6.