1. C. Friedel and J. M. Crafts, Ann. 136, 203 (1865).
2. F. S. Kipping, J. Soc. Chem. Ind. 55, 229T (1937).
3. E. G. Rochow, U.S. Patent No. 2, 380, 995 (1945).
4. J. A. C. Watt, Chem. Brit. 6, 519 (1970).
5. B. A. Bluestein, U.S. Patent No. 3,435, 000 (1969).