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[2] JOHNS HOPKINS MED INST,DEPT NEUROL,BALTIMORE,MD 21205
[3] JOHNS HOPKINS MED INST,DEPT NEURORADIOL,BALTIMORE,MD 21205
[4] UNIV ALBERTA,DEPT NEUROSURG,EDMONTON T6G 2E1,ALBERTA,CANADA
[5] WAKE FOREST UNIV,BOWMAN GRAY SCH MED,DEPT NEUROSURG,WINSTON SALEM,NC 27103
[6] UNIV N CAROLINA,DEPT NEUROSURG,CHAPEL HILL,NC 27514
[7] UNIV MINNESOTA,DEPT NEUROSURG,MINNEAPOLIS,MN 55455