@article{GDZPPN002333074,
title = {Approximations of Sobolev maps between an open set and an Euclidean sphere, boundary data, and singularities.},
journal = {Mathematische Annalen},
volume = {283},
year = {1989},
pages = {125-140},
zbl = {0659.35002},
url = {http://dml.mathdoc.fr/item/GDZPPN002333074}
}
Hélein, Frédéric. Approximations of Sobolev maps between an open set and an Euclidean sphere, boundary data, and singularities.. Mathematische Annalen, Tome 283 (1989) pp. 125-140. http://gdmltest.u-ga.fr/item/GDZPPN002333074/