1. W. H. Organization, WHO Study on global ageing and adult health (SAGE), http://www.who.int/news-room/facts-in-pictures/detail/ageing, (2018, 28 February).
2. Population, National Bureau of Statistics of China, http://data.stats.gov.cn/easyquery.htm?cn=C01&zb=A030707&sj=2016.
3. W. H. Organization, WHO Study on global AGEing and adult health (SAGE), http://www.who.int/healthinfo/sage/en/ (accessed Oct 19, 2015).
4. Chinese Longitudinal Healthy Longevity Survey (CLHLS), https://sites.duke.edu/centerforaging/programs/chinese-longitudinal-healthy-longevity-survey-clhls/.
5. China Health and Retirement Longitudinal Study (CHARLS), http://charls.pku.edu.cn/en.