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2. Das, J., and S. Banerjee: Z. analyt. Chem. 184, 110 (1961).
3. Finar, I. L.: Organic Chemistry, Vol. 1, 1st. Edit., Longmans Green & Co. London 1951, p. 119.
4. Finar, I. L.: Organic Chemistry, Vol. 1, 1st. Edit., Longmans Green & Co. London 1951, p. 171.