1. Jaishankar, M., Tseten, T., Anbalagan, N., Mathew, B.B., Beeregowda, K.N.: Toxicity, mechanism and health effects of some heavy metals. Interdiscip. Toxicol. 7(2), 60–72 (2014)
2. Andrea Zander, M.: eHow Contributor, Heavy Metal Poisoning Signs & Symptoms (2012)
3. Hair Dye.
http://www.madehow.com/Vol.3/Hair-Dye.html
4. The Chemistry of Permanent Hair Dyes.
http://www.compoundchem.com/2015/05/14/hair-dyes/
5. How Hair Coloring Works.
http://science.howstuffworks.com/innovation/everyday-innovations/hair-coloring8.htm