%0 Journal Article %A Jan Stochel %T Characterizations of subnormal operators %J Studia Mathematica %D 1990 %P 227-238 %V 97 %N 3 %U http://geodesic.mathdoc.fr/articles/10.4064/sm-97-3-227-238/ %R 10.4064/sm-97-3-227-238 %G en %F 10_4064_sm_97_3_227_238