@article{ZNSL_1973_38_a1,
     author = {A. A. Arkhipova},
     title = {On smoothness of solutions of the problem with obstacle},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {7--9},
     publisher = {mathdoc},
     volume = {38},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1973_38_a1/}
}