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2. D. Baeriswyl, G. Harbeke, H. Kiess, and W. Meyer, in J. Mort and G. Pfister (eds), Electronic Properties of Polymers, Wiley, New York, Chap. 7 (1982).
3. D. Baeriswyl, Helv. Phys. Acta 56, 639 (1983a).
4. D. Baeriswyl, unpublished results (1983b).
5. D. Baeriswyl, J. Phys. (Paris) 44, C3 - 381 (1983c).