1. Cabinet Office, White Paper on Traffic Safety in Japan 2009 (Government of Japan, Tokyo, 2009). http://www8.cao.go.jp/koutu/taisaku/index-t.html
2. National Police Agency Japan, Police white paper (National Police Agency Japan, Tokyo, 2006). http://www.npa.go.jp/hakusyo/h18/honbun/hakusho/h18/pdfindex.html
3. Cabinet Office, Annual Report on the Aging Society 2006 (Government of Japan, Tokyo, 2006). http://www8.cao.go.jp/kourei/english/annualreport/2006/06wp-e.html . Accessed 13 Jun 2008
4. K. Mitobe, T. Akiyama, N. Yoshimura, M. Takahashi, T. Ifukube, J. ITE 51(6), 850 (1997)
5. K. Mitobe, T. Akiyama, N. Yoshimura, M. Takahashi, T. IEE Jpn. 118-A(3), 245 (1998)