1. W. Zawadzki and R. Lassnig: Proceed. 5th Intern. Conf. Electronic Properties of Two-dimensional Systems, Oxford 1983, Surface Science (in print)
2. W. Zawadzki: Solid State Commun. 47, 317 (1983)
3. T. Haavasoja, H.L. Störmer, D.J. Bishop, V. Narayanamurti, A.C. Gossard and W. Wiegmann: in ref. |1|
4. C. Kittel: Introduction to Solid State Physics, 3d Edition (J.Wiley)
5. W. Zawadzki: J. Phys. C: Solid State Physics, Lett. to Editor (in print)