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2. W.P. Ruemmler, “The Recovery of Zinc from Zinc Ash,” AIME Annual Meeting, San Francisco, February 1972; Chemical Engineering, June 12 (1972) p. 70–71.
3. G. Thorsen, “Process for Recovery of Zinc Values from Zinc Waste,” U.S. Patent 3,958,986, 1976; British Patent 1,463,104, 1974.
4. G. Thorsen, “Extraction and Separation of Metals from Solids Using Liquid Cation Exchangers,” U.S. Patent 4,008,134, 1977; British Patent 1,474,944, 1977.
5. A.J. Van der Zeeuw, “Purification of Zinc Calcine Leach Solutions by Exchange Extraction with the Zinc Salt of Versatic Acid,” Hydrometallurgy, 2 (1977) p. 275–284.