1. J.R. Parga and H. Mercado, “Comparative Study of Direct Pressure Oxidation/Cyanidation and a Pyrometallurgical Process for the Recovery of Precious Metals from Sulfide Concentrates,” Proc. 17th IPMI, Precious Metals 1993 (1993), pp. 55–67.
2. See for example, T. Rosenqvist, Principles of Extractive Metallurgy (New York: McGraw-Hill, 1974), pp. 398–399 or Reference 10.
3. H. Valdez, “Lead Battery Markets and Recycling in Mexico and South America,” J. Power Sources, 67 (1997), pp. 219–223.
4. F.V. Valdez (M. Sc. Thesis, Instituto Tecnológico de Saltillo, México, 1994).
5. Z. Szczygiel et al., “The Direct Reduction of Sulfide Minerals for the Recovery of Precious Metals,” JOM, 4 (1998); pp. 55–59.