1. A.H.M. Kipperman: Private communication
2. G. Pananakasis, P. Viktorovitch, J.P. Ponpon: Rev. Phys. Appl. (to be published)
3. W.G. Townsend: Private communication; W.G. Townsend, D.R. Lillington: In Photovoltaic Solar Energy, Conference, ed. by A. Strab (D. Reidel, Dodrecht, Holland 1977) pp. 207–213
4. J.K. Kim, W.A. Anderson, A.E. Delahoy J. Elec. Mtls.7, 413–414 (1978)
5. H.C. Card: Solid-State Elec.20, 971–976 (1977)