@article{10_1090_S0894_0347_00_00359_3,
     author = {DeVore, Ronald and Petrova, Guergana},
     title = {The averaging lemma},
     journal = {Journal of the American Mathematical Society},
     pages = {279--296},
     publisher = {mathdoc},
     volume = {14},
     number = {2},
     year = {2001},
     doi = {10.1090/S0894-0347-00-00359-3},
     url = {http://geodesic.mathdoc.fr/articles/10.1090/S0894-0347-00-00359-3/}
}