1. R.P. Bell, “The Proton in Chemistry”, 2nd edn., Chapman and Hall, London (1973), chap. 12.
2. E.S. Levis in “Proton-transfer Reactions”, ed. E.F. Caldin and V. Gold, Chapman and Hall, London (1975), Chap. 10.
3. R.P. Bell, Chem. Soc. Rev., 1974, 3, 513.
4. E.F. Caldin Chem. Rev., 1969, 69, 135.
5. E.F. Caldin in “Reaction Transition States”, ed. J.E. Dubois Gordon and Breach, Paris, 1972, pp. 247–255.