1. Chia-yung Chen , “Twenty years of research and development work in retrospect”, ICM, Aca-demia Sinica , Beijing , 1978 , p. 1 .
2. Chia-yung Chen ,in “Hydrometallurgy-Research, Development and Plant Practice”, K. Osseo-Asare and J. D. Miller ed. , AIME , New York , 1983 , p. 65 .
3. D. W. Fuerstenau and S. Raghavan ,in “Advance in Mineral Processing”, P. Somasundaran ed. , AIME/SME , Colorado , 1986 , p. 395 .
4. A. A. Abramov , “Concentrate Technology of Oxidized and Mixed Ores of Nonferrous Metals” (in Russia) , Nedra , Moscow , 1986 , p. 31 .
5. O. B. Klebanov , L. Ya. Shubov and N. K. Shcheglova , “Handbook of Technology on Ore-dressing of Non-ferrous Metals” (in Russian) , Nedra , Moscow , 1974 , p. 291 .