http://www.who.int/water_sanitation_health/dwq/guidelines/en/index.htm
l
http://www.who.int/water_sanitation_health/dwq/dwchem_safety/en/index.
html
http://www.epa.gov/safewater/contaminants/index.html
http://www.copper.org.cn/file/attachment/200865/94354.pdf