1. Z. Burshtein, D.F. Williams, J. Chem. Phys. 66, 2764 (1977)
2. K. Kimura, H. Inokuchi, personal communication (1979)
3. L.E. Lyons, J. Chem. Soc. 5001 (1957)
4. F. Gutmann, L.E. Lyons, “Organic Semiconductors”, Wiley, New York 8, (1967)
5. E. Silinsh, “Electronic States of Organic Molecular Crystals” (in Russian), Zinat., Academy of Science, Latvian SSSR, Riga, (1978)