1. F. W. Gibson, ?Extractive Metallurgy of Lead and Zinc?, Vol. II, AIME (1970) p. 755.
2. Staff, Bureau of Mines, Washington, D.C., Information Circular 8527, U.S. Department of Interior, Bureau of Mines (1971) p. 27.
3. A. E. Moriss and R. Fernandez, ?A New Process for the Direct Smelting of Lead Concentrates?, AIME Annual Meeting, Dalas, Texas (1974).
4. P. E. Queneau and R. Schuhmann,J. Metals 26 (8) (1974) 14.
5. J. B. Brodie, M. S. Thesis, University of British Columbia (1969).