1. See e.g. the review by F. Koch, in: Festkörperproblem/Advances in Solid State Physics XV, ed. by H. J. Queisser (Pergamon, Vieweg, Braunschweig 1975), p. 79
2. W. Hansen, J. P. Kotthaus, A. Chaplik, and K. Ploog, in: High Magnetic Fields in Semiconductor Physics, Proc. of the Int. Conf. Würzburg 1986, ed. by G. Landwehr (Springer, Berlin 1987), p. 266; W. Hansen PhD Thesis, University of Hamburg 1987
3. K. von Klitzing, G. Dorda, and M. Pepper, Phys. Rev. Lett 45, 494 (1980)
4. F. Kuchar, R. Meisels, G. Weimann, and W. Schlapp, Phys. Rev. B33, 2965 (1986)
5. V. A. Volkov, D. V. Galchenkov, L. A. Galchenkov, I. M. Grodnenskii, O. R. Matov, S. A. Mikhailov, A. P. Senichkin, and K. V. Starostin, JETP Lett. 43, 328 (1986) [russian original: Pis'ma Zh. Eksp. Teor. Fiz. 43, 255 (1986)]