%0 Journal Article %T Lectures presented at Winter school. Section of analysis %J Acta Universitatis Carolinae. Mathematica et Physica %D 1999 %P 23-24 %V 40 %N 2 %I mathdoc %U https://geodesic-test.mathdoc.fr/item/AUCMP_1999__40_2_a2/ %G en %F AUCMP_1999__40_2_a2