1. There are severals review books and articles on the density-functional theory: (a) Theory of the Inhomogeneous Electron Gas, S. Lundvist and N. H. March (eds.) (Plenum, New York, 1983) (b) R. M. Dreizler and J. da Providencia, (eds.) Density Functional Methods in Physics, NATO ASI Series B, Vol. 123 (Plenum, New York, 1985); (c) R. O. Jones and O. Gunnarson, Rev. Mod. Phys. 61, 689 (1989); (d) R. M. Dreizler and E. K. U. Gross, Density-Functional Theory (Springer, Berlin etc., 1990); (e) E. K. U Gross and R. M. Dreizler (eds.), Density Functional Theory, NATO ASI Series B, Vol. 337 (Plenum, New York, 1995); (f) H. Eschrig, The Fundamentals of Density Functional Theory (Teubner, Stuttgart, 1996).
2. S. Baroni, P. Giannozzi, and A. Testa, Phys. Rev. Lett. 58, 1861 (1987).
3. N. E. Zein, Fiz. Tverd. Tela 26, 3028 (1984) [Sov. Phys.—Solid State 26, 1825 (1984)].
4. P. Giannozzi, S. de Gironcoli, P. Pavone, and S. Baroni, Phys. Rev. B 43, 7231 (1991).
5. R. D. King-Smith and R. J. Needs, J. Phys. Condens. Matter 2, 3431 (1990).