1. 1) Williams, G.: J. Chem. Soc., 246 (1938)
2. 2) Staudinger, H.; Breusch, F.: Ber., 62B, 442 (1929)
3. 3) Plesch, P. H. Ed.: “The Chemistry of Cationic Polymerization”, Pergamon Press, Oxford (1963)
4. 4) Pepper, D. C.: “Friedel-Crafts and Related Reactions”, Olah, G. A. Ed., Interscience, New York, p.1293 (1964)
5. 5) Higashimura, T.: “Kachion Jugo”, Kagaku Dojin, Kyoto (1971)