@article{RM_1976_31_4_a13,
     author = {I. S. Belov},
     title = {Subharmonicity of the powers of the modulus of the gradient of a~harmonic function},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     publisher = {mathdoc},
     volume = {31},
     number = {4},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1976_31_4_a13/}
}