1. H. BERNS, in ?Proceedings of the International Conference on Tribology in Mineral Extraction: War on Wear?, Nottingham, September 1984 (Mech. Engg. Pub., London, 1984) p. 193.
2. ?Powder Diffraction File, Sets 1?5 (Revised)? (JCPDS, Int. Centre for Diffraction Data, Pennsylvania) p. 467.