@article{MZ_1956__65_169609,
     author = {Hans Sonner},
     title = {\"Uber die {Zur\"uckf\"uhrung} partieller {Differentialgleichnugen} auf gew\"ohnliche.},
     journal = {Mathematische Zeitschrift},
     pages = {483--493},
     publisher = {mathdoc},
     volume = {65},
     year = {1956},
     zbl = {0070.31501},
     url = {http://geodesic.mathdoc.fr/item/MZ_1956__65_169609/}
}