1. http://www.gewater.com/index.jsp
2. www.thewaterexchange.net/fluoride-water-filters.html, www.crystalquest.com
3. http://www.who.int/water_sanitation_health/publications/fluoride_drinking_water_full.pdf
4. http://www.thewaterexchange.net/fluoride-water-filters.htm; http://www.crystalquest.com/data%20sheet%20fluoride.htm
5. Agrawal G (2013) Nonlinear fiber optics, 5th edn. Elsevier, Amsterdam (ISBN 978-0-12-397023-7)