1. Department of Neurology, Dongsan Medical Center, Keimyung University, Daegu, Korea.
2. Korean Sleep Research Society, Seoul, Korea.
3. Department of Neurology, Kyunghee University, East-West Neo Medical Center, Seoul, Korea.
4. Department of Neurology, Inha University Hospital, Incheon, Korea.
5. Department of Neurology, Samsung Medical Center, Sungkyunkwan University, Seoul, Korea.
6. Department of Neurology, Hanyang University Hospital, Seoul, Korea.
7. Department of Neurology, Johns Hopkins University, Hopkins Bayview Medical Center, Baltimore, MD, USA.