@article{MZ_1981__177_173081,
     author = {Peter Sch\"opf},
     title = {Konvexit\"atstreue und {Linearit\"at} von {Abbildungen.}},
     journal = {Mathematische Zeitschrift},
     pages = {533--540},
     year = {1981},
     volume = {177},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/MZ_1981__177_173081/}
}