1. Allman, W.F. Science 85. (October 1985): p. 38.
2. Beck, J.M., J.F. Engelking, and R.L. Elder. Mining and Mineral Processing Wastes. ed. Fiona Doyle. Littleton, CO: SME, 1990: p. 243.
3. Davey, T.R.A. The Physical Chemistry of Lead Refining. Lead-Zin-Tin ’80. eds. J.M. Cigan, T.S. Mackey, and T.J. O’Keefe. Warrendale, PA: TMS, 1979: p. 477.
4. de Bettencourt, K. Mining Voice. (July/August 1997): p. 38.
5. Harris, L. Mining Engineering. (August 1992): p. 1000.