@article{MZ_1939__44_168806,
     author = {0., Baier},
     title = {Ein {Approximationsproblem}},
     journal = {Mathematische Zeitschrift},
     pages = {293--305},
     year = {1939},
     volume = {44},
     zbl = {64.0360.02},
     url = {http://geodesic.mathdoc.fr/item/MZ_1939__44_168806/}
}