1. 1) Ministry of Health, Labour and Welfare (2002) Survey on State of Employees' Health. The institute of labor administration, Statistics and Information Department, Minister's Secretariat, Ministry of Health, Labour and Welfare, Tokyo (in Japanese).
2. 2) Ministry of Health, Labour and Welfare (2000) Debrief report of regular health check-ups. Ministry of Health, Labour and Welfare, Tokyo (in Japanese).
3. 3) Ministry of Internal Affairs and Communications (2001) Establishment and Enterprise Census. Statistics Bureau, Ministry of Internal Affairs and Communications, Tokyo (in Japanese).
4. 4) Ethical Guidelines for Epidemiological Research (2002) Ministry of Education, Culture, Sports, Science and Technology, Ministry of Health, Labour and Welfare, Tokyo.