%0 Journal Article %A Derek Kitson %T Ascent and descent for sets of operators %J Studia Mathematica %D 2009 %P 151-161 %V 191 %N 2 %U http://geodesic.mathdoc.fr/articles/10.4064/sm191-2-3/ %R 10.4064/sm191-2-3 %G en %F 10_4064_sm191_2_3