@article{JRAM_1979__306_152102,
     author = {Stephan Luckhaus},
     title = {Existence and regularity of weak solutions to the {Dirichletproblem} for semilinear elliptic systems of higher order.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {192--207},
     publisher = {mathdoc},
     volume = {306},
     year = {1979},
     zbl = {0395.35026},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1979__306_152102/}
}