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2. Alexandrov, V.B.: Experimental Research in Mineralogy and Geochemistry of Rare Elements, Moscow: Nauka, 1967. (In Russian)
3. Alexandrov, V.B., Kurova, G.A., Ugryumov, D.G.: Conference on the Use of X-rays for Investigation of Materials, Report Theses, p. 275. Moscow 1971. (In Russian)
4. Barinsky, R.L., Kulikova, I.M., Lipatova, N.P.: The investigation of symmetry and effective charges in complex compounds of niobium according to X-ray spectra. Zh. Struct. Khim. 13, 1090?1094 (1972). (In Russian)
5. Barinsky, R.L., Kulikova, I.M., Barskaya, I.B., Toptygina, G.M.: The investigation of excited states of niobium and zirconium complexes according to L III-absorption spectra. Izv. AN SSSR, Ser. Fiz. 38, 516?521 (1974). (In Russian)