4Mukhopaclhyay M, Lim K J, Fairlie FM. Is propess a better method of induction of labor in nulliparous women [ J ] . J Obstet Gynaecol, 2002, 22 (3): 294.
5Grane JM, Bennett KA. A meta - analysis of controlled - release prostagland in for cervical ripening and labour induction [J]. J SOGC, 2000, 22 (9): 692.