1. Four billion people facing severe water scarcity
2. Science and technology for water purification in the coming decades
3. R. W. Hofste , S.Kuzma , S.Walker , E. H.Sutanudjaja , M. F. P.Bierkens , M. J. M.Kuijper , M. F.Sanchez , R. V.Beek , Y.Wada , S. G.Rodriguez and P.Reig , Aqueduct 3.0: Updated Decision-Relevant Global Water Risk Indicators, https://www.wri.org/publication/aqueduct-30 , (accessed 11 November 2020)
4. Desalination for a circular water economy
5. GDP per capita (current US$), https://data.worldbank.org/indicator/NY.GDP.PCAP.CD?end=2019&start=1960&view=chart , (accessed 11 November 2020)