1. Graduate School The Catholic University of Korea, Seoul Metropolitan Rapid Transit Corporation of Korea, Korea.
2. Department of Preventive Medicine and Industrial Medical Center, The Catholic University of Korea, Korea.
3. Department of psychiatry, Seoul St. Mary Hospital, The Catholic University of Korea, Korea.
4. Department of Preventive Medicine, Institute of Occuaptional & Environmental Medicine, Wonju College of Medicine, Yonsei University, Korea.