@article{MZ_1928__27_167969,
     author = {W., Haack},
     title = {Eine {Kennzeichnung} der {Fl\"achen} konstanten {Kr\"ummungsma{\ss}es}},
     journal = {Mathematische Zeitschrift},
     pages = {134--137},
     publisher = {mathdoc},
     volume = {27},
     year = {1928},
     zbl = {53.0661.03},
     url = {http://geodesic.mathdoc.fr/item/MZ_1928__27_167969/}
}