1. Clinical Trials Unit; Office of the Clinical Director, National Institutes of Neurological Disorders and Stroke, National Institutes of Health; Bethesda Maryland USA
2. DINOGMI University of Genoa; Genoa Italy
3. Department of Neurology, Imperial College London; Charing Cross Hospital; London United Kingdom
4. Department of Neurology; Nottingham University Hospitals NHS Trust; Nottingham United Kingdom
5. Department of Neurology; University Hospital “12 de Octubre”; Madrid Spain
6. Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED); Madrid Spain
7. Department of Medicine; Complutense University; Madrid Spain
8. Sobell Department for Movement Neuroscience; UCL, Institute of Neurology; Queen Square London United Kingdom
9. Department of Neurology; Christian-Albrechts-University Kiel; Kiel Germany
10. National School of Public Health and Red de Investigación en Servicios Sanitarios y Enfermedades Crónicas (REDISSEC); Carlos III Institute of Health; Madrid Spain
11. Human Motor Control Section; National Institute of Neurological Disorders and Stroke; National Institutes of Health; Bethesda Maryland USA
12. Departments of Neurology and Chronic Disease Epidemiology; Yale School of Medicine and Yale School of Public Health; Yale University; New Haven Connecticut USA
13. University of Kansas Medical Center; Kansas City Kansas
14. Parkinson's disease and Movement Disorders Center; Division of Neurology; Department of Medicine; University of Ottawa, The Ottawa Hospital Research Institute, Ottawa Brain and Mind Research Institute; Ottawa Ontario Canada
15. Neurology Department; University of Athens, Greece and Neurology Department, Philipps University; Marburg Germany
16. Department of Neurology; National Neuroscience Institute (SGH campus), Duke NUS Medical School, Singapore General Hospital; Singapore
17. Department of Neurology and Parkinson's and Movement Disorders Center; Virginia Commonwealth University; Richmond Virginia USA
18. Department of Neurology; Southern Illinois University School of Medicine; Springfield Illinois USA