@article{IM2_1991_37_3_a1,
     author = {A. V. Babin},
     title = {On the smoothness of solutions of differential equations at singular points of the boundary of the domain},
     journal = {Izvestiya. Mathematics },
     pages = {489--510},
     publisher = {mathdoc},
     volume = {37},
     number = {3},
     year = {1991},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1991_37_3_a1/}
}