@article{MAN_1973__203_162440,
     author = {Peter Volkmann},
     title = {\"Uber die {Invarianz} konvexer {Mengen} und {Differentialunglei} chungen in einem normierten {R\"aume.}},
     journal = {Mathematische Annalen},
     pages = {201--210},
     publisher = {mathdoc},
     volume = {203},
     year = {1973},
     zbl = {0251.34039},
     url = {http://geodesic.mathdoc.fr/item/MAN_1973__203_162440/}
}