Festkörperprobleme 23 Plenary Lectures of the Divisions "Semiconductor Physics" "Metal Physics" "Low Temperature Physics" "Thermodynamics and Statistical Physics" "Thin Films" "Surface Physics" "Surface Physics" "Magnetism" of the German Physical Society (DPG) Freudenstadt, March 21.–25., 1983 - Grosse, P. (Springer Berlin Heidelberg, 1983)