Widths of weighted Sobolev classes on the ball.

Heping Wang Hongwei Huang Widths of weighted Sobolev classes on the ball. 126-139 2008 154 Journal of Approximation Theory 2 http://dx.doi.org/10.1016/j.jat.2008.10.001 db/journals/jat/jat154.html#WangH08