1. Center for Sleep and Circadian Neurobiology and Division of Sleep Medicine/Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA
2. Department of Respiratory Medicine and Sleep, Landspitali – The National University Hospital, Iceland
3. Faculty of Medicine, University of Iceland, Iceland
4. Department of Exploratory and Translational Sciences, Merck Research Laboratories, West Point, PA
5. Biostatistics Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC
6. Neuroscience Department, Merck Research Laboratories, West Point, PA