1. Zelms, J.F., Lead in the 1990’s, Continuing growth or beginning of the end?. In: Lead, Zinc’90, Proc. of the World Symp. on Pb and Zn, Mackey, T.S. and Prengaman, R.D. (Eds.), TMS-AIME, Warrendale, Pa (1990), pp. 5 – 11.
2. Elgersma, F., unpublished results (1990).
3. Elgersma, F., Integrated hydrometallurgical jarosite treatment. Ph.D. thesis, Delft University of Technology (1992).
4. Rodier, D.D., An overview of silver and trace metal recovery strategies in the zinc industry. Ibid [1], pp. 57 – 85.
5. Witkamp, G.J., Crystallization of calcium sulfate and uptake of impurities. Ph.D. thesis, Delft University of Technology (1989).