1. Department of Neurology; Vanderbilt University School of Medicine; Nashville Tennessee USA
2. Department of Neurology; Medical University of Innsbruck; Innsbruck Austria
3. Johns Hopkins University; Baltimore Maryland USA
4. Institute for Medical Research and Sleep Medicine; Schwerin Germany
5. Department of Neurology; University of Rostock; Rostock Germany
6. National Parkinson Foundation Center of Excellence; Kings College London United Kingdom
7. Sleep Research Institute; Madrid Spain
8. Department of Psychiatry; Yale University; New Haven Connecticut USA
9. University of Illinois School of Medicine and Carle Foundation Hospital; Urbana Illinois USA
10. Department of Neurology; Georg-August University; Goettingen Germany
11. National Center of Epidemiology and CIBERNED; Carlos III Institute of Health; Madrid Spain
12. UCL Institute of Neurology; University College; London United Kingdom
13. Department of Neurological Sciences; Rush University Medical Center; Chicago Illinois USA