1. Peierls, R.E.: Quantum theory of solids. p. 108. Oxford Oxford University Press 1955
2. For a review see: Gr�ner, G., Zettl, A.: Phys. Rep.119, 117 (1985)
3. For a review see: Monceau, P. (ed.): In Electronic properties of inorganic quasi-one-dimensional materials. Vol. 2, pp. 139?268. Dordrecht: D. Reidel Publishing Comp. 1985
4. Mayr, W., Philipp, A., Seeger, K.: J. Phys. E.19, 135 (1986)
5. Philipp, A., Mayr, W., Seeger, K.: Physica143B, 27 (1986)