1. Births: final data for 2002. National Center for Health Statistics;Martin;Natl Vital Stat Rep,2003
2. Assessment of fetal lung maturity. ACOG Educational Bulletin No. 230,1996
3. Variation in the length of labor;Calkins;Am J Obstet Gynecol,1930
4. Elective induction of labor;Bishop;Obstet Gynecol,1955
5. Cervical ripening: a review and recommendations for clinical practice;Poma;J Reprod Med,1999