1. I. A. Shiklomanov , in Water in Crisis A Guide to the World's Fresh Water Resources , ed. P. H. Gleick , Oxford University Press , 1993 , pp. 13–24
2. IEA , Water- Energy Nexus , 2016
3. Global Hydrological Cycles and World Water Resources
4. The residence time of water in the atmosphere revisited
5. A. Brown and M. D.Matlock , A Review of Water Scarcity Indices and Methodologies, Sustain. Consort. , 2011 , p. 19