1. T. Ando, H. Fowler, F. Stern, Rev. Mod. Phys. 54, 437 (1982)
2. J.J. Quinn, P.J. Styles (eds.), Electronic Properties of Quasi Two Dimensional Systems (North Holland, Amsterdam, 1976)
3. G.A. Antcliffe, R.T. Bate, R.A. Reynolds, in Proceedings of the International Conference, Physics of Semi-metals and Narrow-Gap semiconductors, vol. 499, ed. By D.L. Carter, R.T. Bate (Pergamon Press, Oxford, 1971)
4. Z.A. Weinberg, Sol. Stat. Electron. 20, 11 (1977)
5. G. Paasch, T. Fiedler, M. Kolar, I. Bartos, Phys. Stat. Sol. (b) 118, 641 (1983)