1. World Population Prospects: The 2019 Revision (XLS)
https://reliefweb.int/sites/reliefweb.int/files/resources/WPP2019_Highlights.pdf
2. The United Nations World Water Development Report 2019: Leaving No One Behind
https://en.unesco.org/themes/water-security/wwap/wwdr/2019
3. Drinking water contamination and treatment techniques
4. Groundwater Pollution: Sources, Mechanisms, and Prevention. Reference Module in Earth Systems and Environmental Sciences;Postigo,2018
5. The Ten Books on Architecture, Book II;Pollio,1914