Surgical versus nonsurgical treatment for lumbar degenerative spondylolisthesis. - Weinstein JN; Lurie JD; Tosteson TD; Hanscom B; Tosteson ANA; Blood EA; Birkmeyer NJO; Hilibrand AS; Herkowitz H; Cammisa FP; Albert TJ; Emery SE; et al. (New England Journal of Medicine, 2007)