@article{DAN_1971_199_3_a3,
     author = {V. E. Kashkakha},
     title = {On the zeros of the gradient of the solutions of second-order homogeneous elliptic equations in the plane},
     journal = {Doklady Akademii Nauk},
     pages = {523--525},
     publisher = {mathdoc},
     volume = {199},
     number = {3},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_199_3_a3/}
}