@article{MZ_1935__39_168562,
     author = {H. Boerner},
     title = {Zur {Theorie} der zweiten {Variation}},
     journal = {Mathematische Zeitschrift},
     pages = {492--500},
     publisher = {mathdoc},
     volume = {39},
     year = {1935},
     zbl = {61.0549.02},
     url = {http://geodesic.mathdoc.fr/item/MZ_1935__39_168562/}
}