1. Muetterties, E.L., Knoth, W.H.: in: Polyhedral Boranes, Wiley & Sons: New York, 1968.
2. Samsonov, G.V., Serebryakova, T.I., Neronov, V.A.: in: Boridy, Moskva Atomzidat, 1975.
3. Wilkins, M.L.: in: Boron and Refractory Borides, V.I. Matkovich ed., Springer: Berlin, Heidelberg, New York, 1977, p. 633.
4. Popescu, M.A.: J. Non-Cryst. Solids 35–36 (1979) 561.
5. Rogl, P., Nowotny, H.: in: Rare earths in modern science and technology, Vol. 2, Proc. 14th rare earth research conf., G.J. McCarthy, J.J., Rhyne, H.B. Silber, ed., Plenum Press: New York, 1980, p. 173.