1. J.G. Heyes & R.G.R. Sellors, Metals & Materials, Feb. 1992, p. 86
2. N.E. Promisel ed, “Science & Technology of Tungsten, Tantalum, Molybdenum, Niobium and their Alloys”, 1964, Pergamon Press, London
3. G.D. Mc.Adam, J.Inst.Met. 93, 1964, p. 559
4. J.E. Restall, Metals & Materials 1, 1967, p. 241
5. D.J. Jones, Metall.Mater.Tech. 5, 1973, p. 503