@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/