1. Department of Clinical Neurosciences University of Calgary Calgary AB Canada
2. Department of Community Health Sciences University of Calgary Calgary AB Canada
3. Department of Neurology Rijnstate Hospital Arnhem The Netherlands
4. Multiple Sclerosis Center Swedish Neuroscience Institute Seattle WA USA
5. Department of Neurology MS Center AmsterdamAmsterdam University Medical Centers Amsterdam The Netherlands
6. Department of Biostatistics University of Alabama at Birmingham Birmingham AL USA