1. E. Hesford, E. E. Jackson, and H. A. C. McKay, J. Inorg. Nucl. Chem. 9, 279 (1959).
2. G. V. Korpusov and E. N. Patrusheva, Rare Earth Elements. Extraction Methods for the Separation of Rare Earth Elements (Nauka, Moscow, 1963) [in Russian].
3. Chemistry and Technology of Rare and Trace Elements, Part 2, Ed. by K. A. Bolshakov (Vyssh. Shkola, Moscow, 1978).
4. E. G. Polyakov, A. V. Nechaev, and A. V. Smirnov, Metallurgy of Rare-Earth Elements (Metallurgizdat, Moscow, 2018) [in Russian].
5. V. V. Kurysheva, E. A. Ivanova, and P. E. Prokhorva, Chim. Technol. Acta 3, 97 (2016).