1. Cabinet Office of Japan White Paper on Suicide Prevention 2012
2. National Police Agency of Japan Traffic Accident Fatalities 2012
3. The search for suicide-prevention factors in an area with low suicide rates among the elderly - Local features of the former Kaifu Town in Tokushima Prefecture;Oka;Jpn. Bull. Soc. Psychiatry,2010
4. The search for suicide-prevention factors in an area with low suicide rates - From the results of the questionnaire survey in former Kaifu Town, Tokushima Prefecture;Oka;Jpn. Bull. Soc. Psychiatry,2011
5. The study of characteristics of mutual aid organization in former Kaifu Town of Tokushilna Prefecture, an area with low suicide rate: A comparison between the ‘Hobai- gumi’ in former Kaifu Town and similar organization in other area;Oka;Jpn. J. Community Psychol.,2012