@article{10_2307_121086,
     author = {Carlos E. Kenig and Tatiana Toro},
     title = {Free boundary regularity for harmonic measures and {Poisson} kernels},
     journal = {Annals of mathematics},
     year = {1999},
     volume = {150},
     number = {2},
     doi = {10.2307/121086},
     zbl = {0946.31001},
     url = {http://geodesic.mathdoc.fr/articles/10.2307/121086/}
}