@article{MS2_1961__9_165774,
     author = {N.O. Wallin},
     title = {A {Problem} for {Elliptic} {Partial} {Differential} {Operators} {Defined} on an {Arbitrary} {Open} {Set.}},
     journal = {Mathematica Scandinavica},
     pages = {185--196},
     publisher = {mathdoc},
     volume = {9},
     year = {1961},
     zbl = {0118.31102},
     url = {http://geodesic.mathdoc.fr/item/MS2_1961__9_165774/}
}