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@article{AM2_1992__43_1_137468, author = {Jarom{\'\i}r Simsa}, title = {The best {L2-approximation} by finite sums of functions with separable variables.}, journal = {Aequationes mathematicae}, pages = {248--263}, publisher = {mathdoc}, volume = {43}, number = {1}, year = {1992}, zbl = {0759.41027}, url = {http://geodesic.mathdoc.fr/item/AM2_1992__43_1_137468/} }
Jaromír Simsa. The best L2-approximation by finite sums of functions with separable variables.. Aequationes mathematicae, Tome 43 (1992) no. 1, pp. 248-263. http://geodesic.mathdoc.fr/item/AM2_1992__43_1_137468/