1. Daugherty, E.W., Erhard, A.E., Drobnick, J.L., 1973. Oxidation of metal sulfides. German Offenlegungsschrift 2,232,570, February 8.
2. Extraction of metals from sulfide ores with nitric acid;Kennecott Copper;Japan Kokai Tokkyo Koho,1979
3. Kunda, W., 1981. Process for the production of elemental silver from silver chloride or silver sulphate. U.S Patent 4,306,902, December 22.
4. Kunda, W., 1982. Process for the recovery of silver values from silver-containing material which also contains iron and arsenic. U.S. Patent 4,331,469, May 25.
5. Kunda, W., 1983. Process for the production of silver powder from silver chloride, sulphate or sulphide. U.S. Patent 4,388,109, June 14.