1. W. Ryan, ?Non-ferrous extractive metallurgy in the United Kingdom? (Institution of Mining and Metallurgy, London, 1968) p. 194.
2. L. Ramqvist, in ?Modern Developments in powder metallurgy?, edited by H. H. Hausner, Vol. 4 (Plenum Press, New York and London, 1971) p. 75.
3. A. Landsberg andT. T. Campbell,J. Metals,17 (1965) 856.
4. S. H. Gelles andF. K. Roehrig,ibid,24 (1972) 23.
5. F. K. Roehrig andT. R. Wright,Mat. Eng. 74 (1971) 17.