1. For a review see e. g.: and , Electronic Processes in Non-Crystalline Materials, Clarendon Press, Oxford 1971.
2. Models of Disorder, Cambridge University Press. Cambridge 1979.
3. XX. Properties of slow electrons in polar materials
4. Electrons in lattice fields
5. in: Mathematical Methods in Solid State and Superfluid Theory, Ed. and , Oliver & Boyd, Edingburgh/London 1967 (p. 46).