6Okamoto M, Shiratori Y, Yamaji Y, et al. Relationship between age and site of colorectal cancer based on colonoscopy findings [J]. Gastroentest Endosc, 2002,55 (4) : 548-551.
7Arai T,SawabeM,Takubo K,et al. Multiple colorectal cancers in the elderly:a retrospective study of both surgical and autopsy cases[J].J Gastroenterol,2001,36(11):748-752.