Zahran KM, Shahin AY, Abdellah MS, Elsayh KI. Sublingual versus vaginal misoprostol for induction of labor at term: a randomized prospective placebo-controlled study. J Obstet Gynaecol Res. 2009 Dec;35(6):1054–60. doi: 10.1111/j.1447-0756.2009.01030.x. PMID: 20144171.