Affiliation: | 1. Clinical Research Center and Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, U.S.A.;2. Cooperative Studies Program Coordinating Center, Hines VA Hospital, Hines, U.S.A.;3. Division of Biostatistics, Community and Family Medicine, Geisel School of Medicine at Dartmouth, Hanover, U.S.A.;4. Department of Health Studies, The University of Chicago Biological Sciences, Chicago, U.S.A. |