@article{EJDE_2002__2002__a254,
     author = {Yakubov,  Sasun},
     title = {Denseness of domains of differential operators in {Sobolev} spaces},
     journal = {Electronic journal of differential equations},
     year = {2002},
     volume = {2002},
     zbl = {1001.46017},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2002__2002__a254/}
}