@article{GDZPPN00218348X,
title = {On the existence of best approximations and representations in several variables.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {238},
year = {1969},
pages = {152-162},
zbl = {0167.04701},
url = {http://dml.mathdoc.fr/item/GDZPPN00218348X}
}
Sprecher, David A. On the existence of best approximations and representations in several variables.. Journal für die reine und angewandte Mathematik, Tome 238 (1969) pp. 152-162. http://gdmltest.u-ga.fr/item/GDZPPN00218348X/