1. World Health Organization. Guidelines for drinking-water quality;World Health Organization:Geneva; Volume 1, Chapter 8, p. 18. Available:www.who.int/water_sanitation_health/dwq/GDW8rev1and2.pdf?ua=1.
2. Vail, J., France, D., and Lewis, B.Ground Water sampling;United States Environmental Protection Agency:Washington, D. C., March 6, 2013; SESDPROC-301-R3;https://www.epa.gov/sites/production/files/2015-06/documents/Groundwater-Sampling.pdf.