1. Handbook of the physiochemical properties of the elements (ed. Samsonov, G. V)., IFI/Plenum, New York 1968, p. 128.
2. Kechin, V.V., Likhter, A.I.: Phys. Status Solidi (b) 117 (1983) K13.
3. Trerfny, J. U., Peters, D.S., Fox, J. N.: J. Non.-Cryst. Solids 65 (1984) 215.
4. Völklein, F.: Thin Solid Films 191 (1990) 1.