1. World Health Statistics 2016: Monitoring Health for the SDGs, Sustainable Development Goalshttps://www.who.int/gho/publications/world_health_statistics/2016/en/
2. World Population Prospects: The 2015 Revision, Key Findings and Advance Tableshttp://wedocs.unep.org/handle/20.500.11822/18246?show=full
3. 2018 World Population Data Sheet With Focus on Changing Age Structureshttps://www.prb.org/2018-world-population-data-sheet-with-focus-on-changing-age-structures/
4. World Population Ageing 2017 Highlights
5. An Aging World: 2015;He