@article{DAN_1977_233_4_a9,
     author = {A. A. Novruzov},
     title = {On a necessary and sufficient condition for regularity of boundary points for quasi-linear elliptic equations of second order},
     journal = {Doklady Akademii Nauk},
     pages = {547--550},
     publisher = {mathdoc},
     volume = {233},
     number = {4},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1977_233_4_a9/}
}