1. von Bauch, G., Pawlek, R. and Plieth, K. Z. Erzbergbau U. Metallhatenw, 11,1958, 1.
2. Nakamura, S. and Halpern, J. J. Am. Chem. Soc., 83,1961, 4102.
3. Vogel, A .T. “Quantitative Inorganic Analysis”, 2nd ed., Longmans .,Green and Co., Toronto 1951, p. 256.
4. Dodds, W .S ., Stutzman, L. F. and Sollami, B.J. J. Chem. Eng. Data, 1,1956, 92.