1. International Lead-Zinc Study Group Conference, Madrid, 18-23 June 1995.
2. Daniel Martin San Lorenzo and Gustavo Diaz Nogueira, “Hydrometallurgical Treatment of Lead Secondaries: The PLACID Process”, International Lead-Zinc Study Group Conference, Rome, June 1991.
3. R. David Prengaman, “Recovering Lead from Batteries,” JOM, 47 January 1995), pp. 31–33.