@article{01423671,
title = {Regularity of a free boundary with application to the Pompeiu problem.},
journal = {Annals of Mathematics. Second Series},
volume = {151},
year = {2000},
pages = {269-292},
doi = {10.2307/121117},
zbl = {0960.35112},
language = {en},
url = {http://dml.mathdoc.fr/item/01423671}
}
Caffarelli, Luis A.; Karp, Lavi; Shahgholian, Henrik. Regularity of a free boundary with application to the Pompeiu problem.. Annals of Mathematics. Second Series, Tome 151 (2000) pp. 269-292. doi : 10.2307/121117. http://gdmltest.u-ga.fr/item/01423671/