1. Information on http://www.spearheadresearch.org.com.
2. Information on http://ga2.er.usgs.gov/edu/activity-water-content.cfm
3. A.Y. Hoekstra. The Water Footprint of Modern Consumer Society. Oxford: Routledge (2013).
4. P. H. Gleick., Water in Crisis: The World’s Water 2000–2001. Washington, DC: Island Press (2000).
5. APHA AW Standard methods for the examination of water and wastewater (22rd edition, 2012).