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2. Fernelius, C.: Inorganic Synthesis II, 1946 p. 59.
3. Gilman, H.: Organic Synthesis, coll., Vol. I, 1946, p. 421.
4. Hinsbark, O. N., and K. G. Stone: Analyt. Chemistry 28, 334 (1956); cf. Z. analyt. Chem. 153, 313 (1956).
5. Kolthoff, I. M., and R. Belcher: Volumetric Analysis, III, Intersci. Publ. 1957, p. 132.