1. Statistical abstracts on health and welfare in Japan, 2002,2003
2. Statistical abstracts on health and welfare in Japan, 2002,2003
3. Annual report on health, labour and welfare, 2000-2001,2002
4. Heisei 13 Nendo Kokumin Iryo-Hi (National Medical Costs in 2001),2002
5. The effects of regionalization on cost and outcome for one general high-risk surgical procedure;Gordon;Ann Surg,1995