@article{GDZPPN002481650, title = {Best Coapproximation in Normed Linear Spaces.}, journal = {Monatshefte f\"ur Mathematik}, volume = {87}, year = {1979}, pages = {27-44}, zbl = {0421.41017}, url = {http://dml.mathdoc.fr/item/GDZPPN002481650} }
Singer, Ivan; Papini, Pier L. Best Coapproximation in Normed Linear Spaces.. Monatshefte für Mathematik, Tome 87 (1979) pp. 27-44. http://gdmltest.u-ga.fr/item/GDZPPN002481650/