@article{MZ_1955__62_169480,
     author = {Woldemar Barthel},
     title = {Variationsprobleme der {Oberfl\"achenfunktion} in der {Finslerschen} {Geometrie.}},
     journal = {Mathematische Zeitschrift},
     pages = {23--36},
     year = {1955},
     volume = {62},
     zbl = {0064.16403},
     url = {http://geodesic.mathdoc.fr/item/MZ_1955__62_169480/}
}