1. Brosset, C.: Z. Anorg. Allgem. Chem. 238 (1938) 201.
2. Knox, K., Geller, S.: Phys. Rev. 110 (1958) 771.
3. Spencer, E.G., Berger, S.B., Linares, R.C., Lenzo, P.V.: Phys. Rev. Lett. 10 (1963) 236.
4. McKinzie, H., Dance, J.-M., Tressaud, A., Portier, J., Hagenmuller, P.: Mater. Res. Bull. 7 (1972) 673.
5. Miranday, J.-P., Ferey, G., Jacoboni, C., Dance, J.-M., Tressaud, A., de Pape, R.: Rev. Chim. Minér. 12 (1975) 187.