5Miller L, Notter KM. Menstrual reduction with extended use of combined oral contraceptive pills:randomized controlled trial.Obstet Gynecol.2001,98:771-778.
6Michaelsson K,Baron JA,Farahmand BY, et al. Oralcontraceptive use and 3risk of hip fracture:a casecontrol study.Lancet,1999,353: 1481-1484.
7Pasco JA,Kotowicz MA,Henry MJ,et al.Oral contraceptives and bonemineral density:a population-based study. Am J Obstet Gynecol,2000,182:265 -269.
8Riman T,Dickman PW, Nilsson S, et al. Risk factors for invasive epithelial ovarian cancer: results from a Swedish case-control study.Am J Epidemlol,2002, 156(4): 363-373.