1. A. B. Shaevich, Izmeritel'naya Tekhnika, No. 10 (1965); No. 11 (1966).
2. L. Fresenius, Metallund Erz,25, (1928).
3. A. P. Vinogradov, in Coll.: Methods of Analysis of Substances of High Purity [in Russian], Izd-vo ?Nauka? (1965).
4. I. p. Alimarin and Yu. V. Kakovlev, Ibid, p. 8.
5. A. M. Dymov, Technical Analysis of Ores and Metals [in Russian], Metallurgizdat, Moscow (1949).