1. D. Haarer and M.R. Phil pott in: Modern Problems in Solid State Physics eds. V.M. Agranovich and R.M. Hochstrasser (North-Holland, 1982 ).
2. R.H. Batt, C.L. Braun, and J.F. Hornig, J. Chem. Phys. 49, 1967 (1968).
3. R.R. Chance and C.L. Braun, J. Chem. Phys. 59, 2269 (1973); 64, 3573 (1976).
4. L. Onsager, Phys. Rev. 54, 554 (1938).
5. N. Wakayama and D.F. Williams, J. Chem. Phys. 57, 1770 (1972); M. Wittmer and I. Zschokke-Gränacher, ibid 63, 4187 (1975).