1. 2) J .E. Hoffman and Bradford Westrom : HYDROMETALLURGY '94 (SCI, imm) , pp70-105.
2. 3) J. E. Hoffman, K. E. Sutliff, B. A. Wells and D. B. George : Journal of Metals, August (1996) , 42-44 .
3. 4) A. Toariwa and Y. Abe : Journal of MMIJ, 116 (2000) ,484-492.
4. 5) Y. Issiki, H. Sato, H. Nagai and S. Asano : Toku Kai 2012-126952.
5. 6) Bruce F Rimer : Chemistry and Industry, 19 (1974) ,63-66.