%0 Journal Article %A Sergio Segura de León %T Bukhvalov type characterizations of Urysohn operators %J Studia Mathematica %D 1991 %P 199-220 %V 99 %N 3 %U http://geodesic.mathdoc.fr/articles/10.4064/sm-99-3-199-220/ %R 10.4064/sm-99-3-199-220 %G en %F 10_4064_sm_99_3_199_220