1. Agricola G. De Re Metallica. Translated by Hoover & Hoover. Project Gutenberg; 1556.
2. Rohrig B. Smart phones, smart chemistry. ChemMatters, American Chemical Society. 2015;2015:10–12.
3. British Geological Survey. World mineral production 2010–2014; 2016.
4. LME. London metal exchange. 2016.
http://www.lme.com
.
5. Infomine. 2016.
http://www.infomine.com
.