@article{CMUC_1992__33_1_a7,
     author = {Oswald, P.},
     title = {On the boundedness of the mapping $f\to |f|$ in {Besov} spaces},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {57--66},
     publisher = {mathdoc},
     volume = {33},
     number = {1},
     year = {1992},
     mrnumber = {1173747},
     zbl = {0766.46018},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1992__33_1_a7/}
}