1. A. S. GYORGYI, in ?Bioelectronics? (Academic Press, London, 1967) p. 79.
2. M. A. SLIFKIN, in ?Charge transfer interactions of biomolecules? (Academic Press, London, 1971) p. 66.
3. B. ROSENBERG, T. N. MISRA and R. SWITZER,Nature 217 (1978) 423.
4. F. GUTMANN and L. E. LYONS, ?Organic semiconductors? (Wiley, New York, 1967).
5. R. FOSTER, ?Organic charge transfer complexes? (Academic Press, London, 1969).