@article{MM2_1979__28_154627,
     author = {Jens Frehse},
     title = {On {Two-Dimensional} {Quasi-Linear} {Elliptic} {Systems.}},
     journal = {Manuscripta mathematica},
     pages = {21--50},
     publisher = {mathdoc},
     volume = {28},
     year = {1979},
     zbl = {0415.35025},
     url = {http://geodesic.mathdoc.fr/item/MM2_1979__28_154627/}
}