1. Chromium;Morning,1975
2. Tin;Mantell,1970
3. Recovery of Secondary Copper and Zinc in the United States;Carrillo;BuMines IC 8622,1974
4. Southwire (Copper Division), 1980. Personal Communication.
5. Bureau of Mines Research on Resource Recovery;Spendlove;BuMines IC 8750,1977