1. Akkermans, E., Wolf, P.E., Maynard, R., and Maret., G. (1988), J. Phys. (Paris)
49, p. 77.
2. Amic, E., Luck, J.M., and Nieuwenhuizen, Th. M. (1996), J. Phys. A
29, p. 4915.
3. Amic, E., Luck, J.M., and Nieuwenhuizen, Th. M. (1997), J. Phys.
17, p. 445.
4. Boots, H.M.L., Bedeaux, D., and Mazur, P. (1975) Physica
79A, p. 397.
5. Chandrasekhar, S. (1960) Radiation Transfer. Dover, New York.