@article{AM2_1975__12_136508,
     author = {Dietrich Braess},
     title = {On the {Number} of {Best} {Approximation} in {Certain} {Non-linear} {Families} of {Functions.}},
     journal = {Aequationes mathematicae},
     pages = {184--199},
     publisher = {mathdoc},
     volume = {12},
     year = {1975},
     zbl = {0304.41014},
     url = {http://geodesic.mathdoc.fr/item/AM2_1975__12_136508/}
}