1. H. Ibach, H. Lüth, Solid-State Physics, 4th edn. (Springer, Berlin, 2009)
2. A. Many, Y. Goldstein, N.B. Grover, Semiconductor Surfaces (North-Holland, Amsterdam, 1965)
3. H. Lüth, M. Büchel, R. Dorn, M. Liehr, R. Matz, Phys. Rev. B 15, 865 (1977)
4. E. Veuhoff, C.D. Kohl, J. Phys. C, Solid State Phys. 14, 2395 (1981)
5. T. Ando, A.B. Fowler, F. Stern, Electronic properties of two-dimensional systems, in Rev. Mod. Phys., vol. 54 (AIP, New York, 1982), p. 437