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@article{MOMA_1979__88_177926, author = {Ivan Singer and Pier L. Papini}, title = {Best {Coapproximation} in {Normed} {Linear} {Spaces.}}, journal = {Monatshefte f\"ur Mathematik}, pages = {27--44}, publisher = {mathdoc}, volume = {88}, year = {1979}, zbl = {0421.41017}, url = {http://geodesic.mathdoc.fr/item/MOMA_1979__88_177926/} }
Ivan Singer; Pier L. Papini. Best Coapproximation in Normed Linear Spaces.. Monatshefte für Mathematik, Tome 88 (1979), pp. 27-44. http://geodesic.mathdoc.fr/item/MOMA_1979__88_177926/