@article{MM2_1989__63_3_155392,
     author = {R. DeVore and R. Howard and C. Micchelli},
     title = {Optimal nonlinear approximation.},
     journal = {Manuscripta mathematica},
     pages = {469--478},
     publisher = {mathdoc},
     volume = {63},
     number = {3},
     year = {1989},
     zbl = {0682.41033},
     url = {http://geodesic.mathdoc.fr/item/MM2_1989__63_3_155392/}
}