@article{IM2_1989_33_3_a6,
     author = {M. V. Safonov},
     title = {On~the classical solution of nonlinear elliptic equations of second order},
     journal = {Izvestiya. Mathematics },
     pages = {597--612},
     publisher = {mathdoc},
     volume = {33},
     number = {3},
     year = {1989},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1989_33_3_a6/}
}