1. Silver essentials, https://www.silverinstitute.org/silver-essentials/ , accessed 14 November 2017
2. W. C. Butterman and H. E.Hilliard , Mineral Commodity Profiles - Silver , 2005
3. Thomson Reuters, World Silver Survey 2017, https://www.silverinstitute.org/all-world-silver-surveys , accessed 1 June 2017
4. Joint Research Centre, Best available techniques (BAT) reference document for the non-ferrous metals industries, http://eippcb.jrc.ec.europa.eu/reference/nfm.html , accessed 1 July 2017
5. D. Pletcher and F. C.Walsh , Industrial Electrochemistry , Chapman & Hall , 2nd edn, 1990