@article{MZ_1975__142_172183,
     author = {Stefan Hildebrandt and Kjell-Ove Widman},
     title = {Some {Regularity} {Results} for {Quasilinear} {Elliptic} {Systems} of {Second} {Order.}},
     journal = {Mathematische Zeitschrift},
     pages = {67--86},
     publisher = {mathdoc},
     volume = {142},
     year = {1975},
     zbl = {0317.35040},
     url = {http://geodesic.mathdoc.fr/item/MZ_1975__142_172183/}
}