Clark A. H., Phys. Rev. 154 (1967), 750.
Male J. C., Brit. Jour. Appl. Phys.18 (1967), 1543.
Carver G. P., Allgaier R. S., Jour. Non-Cryst. Solids 8–10 (1972), 347.
Callaerts B., Denayer M., Hashmi F. H., Nagels P., Discussions of the Farad. Society50 (1970), 27.
Seager C. H., Emin D., Quinn R. K., Jour. Non-Cryst. Solids8–10 (1972), 341.
Holstein T., Phys. Rev.124 (1961), 1329.
Čápek V., Czech. J. Phys.B 22 (1972), 1122.
Blatt F. J., Physics of Electronic Conduction in Solids (in Russian), Moscow 1971.