%0 Journal Article %A Carlo Cecchini %T An abstract characterization of ...-conditional expectations. %J Mathematica Scandinavica %D 1990 %P 155-160 %V 66 %N 1 %I mathdoc %U http://geodesic.mathdoc.fr/item/MS2_1990__66_1_167101/ %F MS2_1990__66_1_167101