@article{RM_2002_57_4_a1,
     author = {H. Brezis},
     title = {How to recognize constant functions. {Connections} with {Sobolev} spaces},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {693--708},
     publisher = {mathdoc},
     volume = {57},
     number = {4},
     year = {2002},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_2002_57_4_a1/}
}