@article{MAN_1989__283_1_164533,
     author = {Konrad Gr\"oger},
     title = {A {W1,p-Estimate} for {Solutions} to {Mixed} {Boundary} {Value} {Problems} for {Second} {Order} {Elliptic} {Differential} {Equtions.}},
     journal = {Mathematische Annalen},
     pages = {679--688},
     publisher = {mathdoc},
     volume = {283},
     number = {1},
     year = {1989},
     zbl = {0646.35024},
     url = {http://geodesic.mathdoc.fr/item/MAN_1989__283_1_164533/}
}