@article{MZ_1920__8_167588,
     author = {L., Berwald},
     title = {\"Uber affine {Geometrie} {XXVII.} {Liesche} {F2} {Affinnormale} un mittlere {Affinkr\"ummung}},
     journal = {Mathematische Zeitschrift},
     pages = {63--78},
     publisher = {mathdoc},
     volume = {8},
     year = {1920},
     zbl = {47.0661.04},
     url = {http://geodesic.mathdoc.fr/item/MZ_1920__8_167588/}
}