1. VA Portland Health Care System, Oregon Health & Science University, Portland, OR, USA
2. OHSU Biostatistics Design Program, OHSU-PSU School of Public Health, Oregon Health & Science University, Portland, OR, USA
3. VA Puget Sound Health Care System, University of Washington Department of Rehabilitation Medicine, Seattle, WA, USA
4. North Florida/South Georgia Veterans Health System, Gainesville, FL, USA
5. VA Maryland Health Care System, University of Maryland, Department of Neurology Baltimore, MD, USA