@article{COCV_2009__15_1_102_0,
     author = {Castelpietra, Marco},
     title = {Interior sphere property for level sets of the value function of an exit time problem},
     journal = {ESAIM: Control, Optimisation and Calculus of Variations},
     pages = {102--116},
     publisher = {EDP-Sciences},
     volume = {15},
     number = {1},
     year = {2009},
     doi = {10.1051/cocv:2008018},
     mrnumber = {2488570},
     zbl = {1155.49024},
     language = {en},
     url = {http://archive.numdam.org/articles/10.1051/cocv:2008018/}
}