@article{MZ_1980__170_172918,
     author = {Per-Anders Ivert},
     title = {On {Quasilinear} {Elliptic} {Systems} of {Diagonal} {Form.}},
     journal = {Mathematische Zeitschrift},
     pages = {283--286},
     publisher = {mathdoc},
     volume = {170},
     year = {1980},
     zbl = {0411.35006},
     url = {http://geodesic.mathdoc.fr/item/MZ_1980__170_172918/}
}