[1] UNIV MARYLAND,SCH MED,CTR STUDIES REPROD,DEPT OBSTET GYNECOL,BALTIMORE,MD 21201
[2] UNIV MARYLAND,SCH MED,CTR STUDIES REPROD,DEPT PHYSIOL,BALTIMORE,MD 21201
[3] MCGILL UNIV,FAC MED,DEPT OBSTET & GYNAECOL,MONTREAL,PQ,CANADA
[4] EASTERN VIRGINIA MED SCH,DEPT PHYSIOL,NORFOLK,VA 23501