%0 Journal Article %A González-Hernández, Juan %A Hernández-Hernández, Fernando %A Villarreal, César E. %T When is $\Bbb R$ the union of an increasing family of null sets? %J Commentationes Mathematicae Universitatis Carolinae %D 2007 %P 623-630 %V 48 %N 4 %U http://geodesic.mathdoc.fr/item/CMUC_2007_48_4_a5/ %G en %F CMUC_2007_48_4_a5