Voir la notice de l'article provenant de la source European Digital Mathematics Library
@article{MAN_1965__159_182694, author = {I. SINGER}, title = {On the {Extension} of {Continuous} {Linear} {Functionals} and {Best} {Approximation} in {Normed} {Linear} {Spaces.}}, journal = {Mathematische Annalen}, pages = {344--355}, publisher = {mathdoc}, volume = {159}, year = {1965}, zbl = {0141.12002}, url = {http://geodesic.mathdoc.fr/item/MAN_1965__159_182694/} }
I. SINGER. On the Extension of Continuous Linear Functionals and Best Approximation in Normed Linear Spaces.. Mathematische Annalen, Tome 159 (1965), pp. 344-355. http://geodesic.mathdoc.fr/item/MAN_1965__159_182694/