@article{ZNSL_1967_5_a7,
     author = {V. G. Maz'ya and V. P. Havin},
     title = {On approximation in the mean by harmonic functions},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {196--200},
     publisher = {mathdoc},
     volume = {5},
     year = {1967},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1967_5_a7/}
}