@article{MAN_1965__158_161252,
     author = {A. KRISZTEN},
     title = {Zur {Geometrie} der partiellen {Differentialgleichung} 2. {Ordnung.}},
     journal = {Mathematische Annalen},
     pages = {35--45},
     year = {1965},
     volume = {158},
     zbl = {0123.15405},
     url = {http://geodesic.mathdoc.fr/item/MAN_1965__158_161252/}
}