1. Rare Earth Elements;Mikhailichenko,1987
2. Physical and Chemical Study on Processing of Rare Earth Titanoniobates by Sulphuric Acid;Gorostchenko,1960
3. Proc. Symp. on the Recovery of Uranium;Zefirov,1971
4. Complex processing of apatite from the Kola Peninsula;Masloboev,1989
5. Lanthanoids in the Ores of Rare Earths and Complex Deposits;Mineev,1974