@article{GDZPPN002301946, title = {Approximationstheorie f\"ur metrische lineare R\"aume.}, journal = {Mathematische Annalen}, volume = {189}, year = {1970}, pages = {30-48}, zbl = {0175.42001}, url = {http://dml.mathdoc.fr/item/GDZPPN002301946} }
PANTELIDIS, G. Approximationstheorie für metrische lineare Räume.. Mathematische Annalen, Tome 189 (1970) pp. 30-48. http://gdmltest.u-ga.fr/item/GDZPPN002301946/