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@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/} }
E.W. Cheney; D.E. Wulbert. The Existence and Unicity of Best Approximations.. Mathematica Scandinavica, Tome 24 (1969), pp. 113-140. http://geodesic.mathdoc.fr/item/MS2_1969__24_166085/