1. Wear of railway contact wires against current collector materials;He;Wear,1998
2. Effect of arc discharge on the wear rate and wear mode transition of a copper-impregnated metallized carbon contact strip sliding against a copper disk;Kubo;Tribol. Int.,1999
3. Classification chimique des mineraux. Available from: http://www.chez.com/pgosse/gem/chim.htm
4. Engineering fundamentals, Hardness convertion (Vickers versus Mohs). Available from: http://www.efunda.com/units/hardness/convert_hardness.cfm
5. ASM Handbook. Properties and selection: nonferrous alloys and special purpose materials, vol. 2, 1990, ASM International