1. H. Fröhlich:Journ. Collective Phenomena (in press).
2. H. Fröhlich:Physica,37, 215 (1967).
3. H. Fröhlich:Journ. Phys. Soc. Japan,26,Supplement, 189 (1969).
4. G. J. Hyland andG. Rowlands:Phys. Lett.,33 A, 197 (1970).
5. C. Terraux andP. Lal: inCooperative Phenomena, edited byH. Haken (Berlin) (in press).