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4. Cabinet Office. (2009). Heisei 21 survey on lifestyle of community-based older adults. Retrieved from http://www8.cao.go.jp/ .
5. Cabinet Office. (2011a). Heisei 23 white paper on aging society. Retrieved from http://www8.cao.go.jp/kourei/whitepaper/w-2011/zenbun/html/s1-1-1-02.html .