1. Bhatnagar P L, Gross E P and Krook M 1954Phys. Rev. 94 511
2. Chaban A A 1968Sov. Phys.—Solid State 9 2622
3. Ehrenreich H 1966Proc. Int. School of Physics Enrico Fermi Course XXXIV ed. J Tauc (New York: Academic Press) 106
4. Epshtein E M 1969Sov. Phys.—Solid State 10 2325
5. Fried B D and Conte S D 1961The plasma dispersion function (New York: Academic Press)