5Higham JM,O'brien PMS,Show RW.Assessment of menstrual blood loss using a pictorial chart.Br J Obstet Gynecol,1990,97:734-739.
6Vercellini P,Aimi G,Panazza S,et al.A levonorgestrel-releasing intrauterine system for the treatment of dysmenorrhea associated with endometriosis:a pilot study.Fertil Steril,1999,72(3):505-508.
7Crosignani PG,Vercellini P,Mosconi P,et al.Levonorgestrel-releasing intrauterine device versus hysteroscopic endometrial resection in the treatment of dysfunctional uterine bleeding.Obstet Gynecol,1997,90(2):257-263.
8Janssen CA,Scholten PC,Heintz AP.A simple visual assessment technique to discriminate between menorrhagia and normal menstrual blood loss.Obstet Gynecol,1995,85(6):977-982.
9Feinstein AR.Clinical epidemiology:architecture of clinical research.WB Saunders Company,1985,601-632.
10Mishell DR.Intrauterine devices:mechanisms of action,safety,and efficacy.Contraception,1998,58(3):45-53.