@article{CM_1969__21_4_400_0,
     author = {Nitsche, J.},
     title = {Umkehrs\"atze f\"ur {Spline-Approximationen}},
     journal = {Compositio Mathematica},
     pages = {400--416},
     publisher = {Wolters-Noordhoff Publishing},
     volume = {21},
     number = {4},
     year = {1969},
     mrnumber = {259436},
     zbl = {0199.39302},
     language = {de},
     url = {http://www.numdam.org/item/CM_1969__21_4_400_0/}
}