1Haley JC,Perry JH.Protrusion of intervertebral discs:study ofthier distribution,characteristics and effects on the nerves system[J].Am J Surg,1950,8:304.
2Wiesel SW.A study of Computer-assisted tomography:The incidence of postive CAT scans in an asymptomatic group of patients[J].Spine,1984,9:549.