1. Krishnamurthy, N. and Gupta, C.K., Extractive Metallurgy of Rare Earths, New York: CRC, 2016.
2. Kosynkin, V.D., Trubakov, Yu.M., and Sarychev, G.A., Evraz. Nauchn. Ob”edin., 2015, vol. 1, no. 6, p. 49.
3. Redkie i redkozemel’nye metally: tekhnologii, funktsional’nye materialy i primenenie (Rare and Rare Earth Metals. Technologies, Functional Materials, and Applications), Buinovskii, A.S., Kazaryan, M.A., and Sachkov, V.M., Eds., Tomsk: NTL, 2014, p. 14.
4. Zagorodni, A., Ion Exchange Materials: Properties and Applications, Oxford: Elsevier, 2007.
5. US Patent no. 2 366 007, 1944.