1. McLachlan, A.D., and Ball, M.A.: 1964, Revs. Mod. Phys. 36, pp. 844–55.
2. Öhrn, Y., and Linderberg, J.: 1965, Phys. Rev. 139, pp. A1063–68.
3. Thouless, D.J.: 1961, “Quantum Mechanics of Many Body Systems” ( Academic Press, New York).
4. Lindhard, J.: 1954, Kgl. Dan. Vid. Selsk. Mat. Phys. Medd. 28, no 8, pp. 1–57.
5. Dalgarno, A., and Victor, G.A.: 1966, Proc. Roy. Soc. (London) Ser. A 291, pp. 291–5.