8North American Symptomatic Carotid Endarterectomy Trial:Meth-ods.patient characteristics and progress.Stroke,1991,22:711-720.
9North American Symptomatic Carotid Endarterectomy Trial Colla-borators.The benefit of carotid endarterectomy in symptomatic patients with moderate and severe stenosis.N Engl J Med,1998,339:1 415-1 426.