1. Norman, R. and Taylor, R., Electrophilic Substitution in Benzenoid Compounds, Amsterdam: Elsevier, 1965.
2. Carbonium Ions, Olah, G.A. and Schleyer, P.v.R., Eds., New York: Wiley, 1970, vol. 2, p. 837.
3. Olah, G.A., Kuhn, S., and Pavlath, A., Nature, 1956, vol. 178, no.4535, p. 693.
4. Olah, G.A., Schlosberg, R.H., Porter, R.D., Mo, Y.K., Kelley, D.P., and Matescu, G.D., J. Am. Chem. Soc., 1972, vol. 94, no.6, p. 2034.
5. Baenziger, N.C. and Nelson, A.D., J. Am. Chem. Soc., 1968, vol. 90, no.24, p. 6602.