@article{MZ_1976__151_172435,
     author = {Walter Schempp},
     title = {Group {Actions} on the {Solutions} of {Linear} {Partial} {Differential} {Equations.}},
     journal = {Mathematische Zeitschrift},
     pages = {111--116},
     publisher = {mathdoc},
     volume = {151},
     year = {1976},
     zbl = {0328.47025},
     url = {http://geodesic.mathdoc.fr/item/MZ_1976__151_172435/}
}