@article{MS2_1969__24_166085,
     author = {E.W. Cheney and D.E. Wulbert},
     title = {The {Existence} and {Unicity} of {Best} {Approximations.}},
     journal = {Mathematica Scandinavica},
     pages = {113--140},
     publisher = {mathdoc},
     volume = {24},
     year = {1969},
     zbl = {0186.18701},
     url = {http://geodesic.mathdoc.fr/item/MS2_1969__24_166085/}
}