1. Volosova, M.A. and Okun’kova, A.A., Izy. Samarsk. Nauchn. Tsentra Ross. Akad. Nauk, 2012, vol. 14, no. 4, p. 587.
2. Serebrennikov, V.V., Yakunina, G.M., Kozik, V.V., and Sergeev, A.N., Redkozemel’nye elementy i ikh soedineniya v elektronnoi tekhnike (Rare Earth Elements and Their Compounds in Electronic Engineering), Tomsk: Tomsk. Gos. Univ., 1979.
3. Petrakian, J.P., J. Opt. Soc. Am., 1972, vol. 62, no. 3, p. 401.
4. Knyazev, Yu.V., Kirillova, M.M., and Nikitin, S.A., Fiz. Met. Metalloved., 1990, no. 12, p. 33.
5. Knyazev, Yu.V. and Kuz’min, Yu.M., Fiz. Met. Metalloved., 1998, vol. 85, no. 6, p. 80.