@article{MZ_1921__9_167616,
     author = {W., Blaschke},
     title = {\"Uber affine {Geometrie} {XXIX:} {Die} {Starrheit} der {Eifl\"achen}},
     journal = {Mathematische Zeitschrift},
     pages = {142--146},
     publisher = {mathdoc},
     volume = {9},
     year = {1921},
     zbl = {48.0837.01},
     url = {http://geodesic.mathdoc.fr/item/MZ_1921__9_167616/}
}