1. De Grave, E., Dauwe, C., De Sitter, J., Govaert, A.: J. Phys. (Paris) 37 (1976) C6–497.
2. De Grave, E., De Sitter, J., Vandenberghe, R.: Appl. Phys. 7 (1975) 77.
3. Parkhomenko, V.D., Dubinin, S.F., Goshchitskii, B.N., Chukalkin, Yu.G., Sidorov, S.K., Vologin, V.G., Petrov, V.V.: Phys. Status Solidi (a) 38 (1976) 57.
4. Van Diepen, A.M., Popma, T.J.A.: Solid State Commun. 27 (1978) 121.
5. Krishnamurthy, K. R., Viswanathan, B., Sastri, M.V.C.: J. Res. Inst. Catal. 24 (1976) 219.