@article{MZ_1959__71_169813,
     author = {Wolfgang Walter},
     title = {\"Uber die {Differentialgleichung} u... = f (x, y, u, u..., u...).},
     journal = {Mathematische Zeitschrift},
     pages = {308--324},
     publisher = {mathdoc},
     volume = {71},
     year = {1959},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/MZ_1959__71_169813/}
}