@article{DAN_1964_158_3_a12,
     author = {A. Yanushauskas},
     title = {On the zeros of the gradient of a harmonic function},
     journal = {Doklady Akademii Nauk},
     pages = {547--549},
     publisher = {mathdoc},
     volume = {158},
     number = {3},
     year = {1964},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1964_158_3_a12/}
}