1. The Statistics Bureau of the Ministry of Internal Affairs and Communications: The population statistics released in October 2013 (2014)
2. Director General for Policy on Cohesive Society: The white paper on aging society in 2014 (2014)
3. Ministry of Health, Labour and Welfare: Comprehensive survey of living conditions in 2014 (2014)
4. Hasebe, M.: A study of autobiographical memory functions in elderly people who live alone. The Study of Social Work, No.48, 111–114 (2009)
5. Mizuho Information & Research Institute: Business report on surveys and research of community infrastructure and its plan to support in elderly people who live alone and aged household (2012)