1. School of Public Health in the Graduate School of Medicine, Kyoto University; Department of Healthcare Epidemiology; Yoshida Konoe-cho, Sakyo-ku Kyoto Japan 606-8501
2. Hyogo Prefectural Amagasaki General Medical Center; Hospital Care Research Unit; Higashi-Naniwa-Cho 2-17-77 Amagasaki Hyogo Japan 606-8550
3. Shimane University; Department of Mathematics; 1060 Nishikawatsu cho Matsue 690-8504 Japan